diff --git a/src/main/java/jobshop/encodings/ResourceOrder.java b/src/main/java/jobshop/encodings/ResourceOrder.java
index cbc2a61..02b8983 100644
--- a/src/main/java/jobshop/encodings/ResourceOrder.java
+++ b/src/main/java/jobshop/encodings/ResourceOrder.java
@@ -72,6 +72,22 @@ public final class ResourceOrder extends Encoding {
         return tasksByMachine[machine][taskIndex];
     }
 
+    /** Returns the index of a particular task scheduled on a particular machine.
+     *
+     * @param machine Machine on which the task to retrieve is scheduled.
+     * @param task Task in the queue for this machine.
+     * @return The index of the task scheduled on a machine.
+     */
+    public int getIndexOfTaskOnMachine(int machine, Task task) {
+        int i = 0;
+        boolean found = false;
+        while (i<instance.numJobs && !found) {
+            found = getTaskOfMachine(machine, i).equals(task);
+            i++;
+        }
+        return i - 1;
+    }
+
     /** Exchange the order of two tasks that are scheduled on a given machine.
      *
      * @param machine Machine on which the two tasks appear (line on which to perform the exchange)
diff --git a/src/main/java/jobshop/solvers/DescentSolver.java b/src/main/java/jobshop/solvers/DescentSolver.java
index 8585d8e..a6ca4d1 100644
--- a/src/main/java/jobshop/solvers/DescentSolver.java
+++ b/src/main/java/jobshop/solvers/DescentSolver.java
@@ -3,7 +3,17 @@ package jobshop.solvers;
 import jobshop.Instance;
 import jobshop.Result;
 import jobshop.encodings.ResourceOrder;
+import jobshop.encodings.Schedule;
+import jobshop.solvers.neighborhood.Neighbor;
 import jobshop.solvers.neighborhood.Neighborhood;
+import jobshop.solvers.neighborhood.Nowicki;
+
+import java.io.IOException;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.stream.Collectors;
 
 /** An empty shell to implement a descent solver. */
 public class DescentSolver implements Solver {
@@ -23,7 +33,39 @@ public class DescentSolver implements Solver {
 
     @Override
     public Result solve(Instance instance, long deadline) {
-        throw new UnsupportedOperationException();
+        Schedule schedule = baseSolver.solve(instance, deadline).schedule.get();
+        ResourceOrder resourceOrder = new ResourceOrder(schedule);
+        boolean ended = false;
+        int bestMakespan;
+        Neighbor<ResourceOrder> bestNeighbor;
+
+        while (!ended) {
+            schedule = resourceOrder.toSchedule().get();
+            bestMakespan = schedule.makespan();
+            bestNeighbor = null;
+            List<Neighbor<ResourceOrder>> generatedNeighbors = neighborhood.generateNeighbors(resourceOrder);
+            Iterator<Neighbor<ResourceOrder>> iter = generatedNeighbors.iterator();
+            while (iter.hasNext()) {
+                Neighbor<ResourceOrder> neighbor = iter.next();
+                neighbor.applyOn(resourceOrder);
+                try {
+                    Schedule currentSchedule = resourceOrder.toSchedule().get();
+                    int currentMakespan = currentSchedule.makespan();
+                    if (currentMakespan < bestMakespan) {
+                        bestMakespan = currentMakespan;
+                        bestNeighbor = neighbor;
+                    }
+                } catch (Exception e) {
+                }
+                neighbor.undoApplyOn(resourceOrder);
+            }
+            if (bestNeighbor == null) {
+                ended = true;
+            } else {
+                bestNeighbor.applyOn(resourceOrder);
+            }
+        }
+        return new Result(instance, resourceOrder.toSchedule(), Result.ExitCause.ProvedOptimal);
     }
 
 }
diff --git a/src/main/java/jobshop/solvers/GreedySolver.java b/src/main/java/jobshop/solvers/GreedySolver.java
index 7382205..aea875c 100644
--- a/src/main/java/jobshop/solvers/GreedySolver.java
+++ b/src/main/java/jobshop/solvers/GreedySolver.java
@@ -23,6 +23,9 @@ public class GreedySolver implements Solver {
     final Priority priority;
 
     final ArrayList<Task> tachesRestantes;
+    int[] machineFreeDate;
+    int[] jobFreeDate;
+
 
 
     /** Creates a new greedy solver that will use the given priority. */
@@ -31,8 +34,12 @@ public class GreedySolver implements Solver {
         this.tachesRestantes = new ArrayList<>();
     }
 
+    private int getEarliestDate(Instance instance, Task task) {
+        return Math.max(machineFreeDate[instance.machine(task)], jobFreeDate[task.job]);
+    }
+
     /** return true if t1 est plus prioritaire que t1 **/
-    private boolean prioritaire(Instance instance, Task t1, Task t2) throws Exception {
+    private boolean prioritaire(Instance instance, Task t1, Task t2) {
         boolean rt = false;
         switch(priority) {
             case SPT:
@@ -65,51 +72,107 @@ public class GreedySolver implements Solver {
                 rt = sigmaT1 >= sigmaT2;
                 break;
             case EST_SPT:
-                throw new Exception("UNKNOWN PRIORITY");
-                //break;
+                if (getEarliestDate(instance, t1) < getEarliestDate(instance, t2)) {
+                    rt = true;
+                } else if (getEarliestDate(instance, t1) > getEarliestDate(instance, t2)) {
+                    rt = false;
+                } else {
+                    rt = instance.duration(t1) <= instance.duration(t2);
+                }
+                break;
             case EST_LPT:
-                throw new Exception("UNKNOWN PRIORITY");
-                //break;
+                if (getEarliestDate(instance, t1) < getEarliestDate(instance, t2)) {
+                    rt = true;
+                } else if (getEarliestDate(instance, t1) > getEarliestDate(instance, t2)) {
+                    rt = false;
+                } else {
+                    rt = instance.duration(t1) >= instance.duration(t2);
+                }
+                break;
             case EST_SRPT:
-                throw new Exception("UNKNOWN PRIORITY");
-                //break;
+                if (getEarliestDate(instance, t1) < getEarliestDate(instance, t2)) {
+                    rt = true;
+                } else if (getEarliestDate(instance, t1) > getEarliestDate(instance, t2)) {
+                    rt = false;
+                } else {
+                    sigmaT1 = 0;
+                    sigmaT2 = 0;
+                    for (i=t1.task; i<instance.numTasks; i++) {
+                        sigmaT1 += instance.duration(t1.job, i);
+                    }
+                    for (i=t2.task; i<instance.numTasks; i++) {
+                        sigmaT2 += instance.duration(t2.job, i);
+                    }
+                    rt = sigmaT1 <= sigmaT2;
+                }
+                break;
             case EST_LRPT:
-                throw new Exception("UNKNOWN PRIORITY");
-                //break;
+                if (getEarliestDate(instance, t1) < getEarliestDate(instance, t2)) {
+                    rt = true;
+                } else if (getEarliestDate(instance, t1) > getEarliestDate(instance, t2)) {
+                    rt = false;
+                } else {
+                    sigmaT1 = 0;
+                    sigmaT2 = 0;
+                    for (i=t1.task; i<instance.numTasks; i++) {
+                        sigmaT1 += instance.duration(t1.job, i);
+                    }
+                    for (i=t2.task; i<instance.numTasks; i++) {
+                        sigmaT2 += instance.duration(t2.job, i);
+                    }
+                    rt = sigmaT1 >= sigmaT2;
+                }
+                break;
         }
         return rt;
     }
 
-    private void addTask(Instance instance, Task task) throws Exception {
-        Iterator<Task> iter = this.tachesRestantes.iterator();
-        int index = 0;
-        boolean trouve = false;
-        while (iter.hasNext() && !trouve) {
-            Task current = iter.next();
-            if (this.prioritaire(instance, task, current)) {
-                trouve = true;
-            } else {
-                index++;
+    private void addTask(Instance instance, Task task) {
+        if (priority == Priority.SPT || priority == Priority.LPT || priority == Priority.SRPT || priority == Priority.LRPT) {
+            Iterator<Task> iter = this.tachesRestantes.iterator();
+            int index = 0;
+            boolean trouve = false;
+            while (iter.hasNext() && !trouve) {
+                Task current = iter.next();
+                if (this.prioritaire(instance, task, current)) {
+                    trouve = true;
+                } else {
+                    index++;
+                }
             }
+            this.tachesRestantes.add(index, task);
+        } else {
+            this.tachesRestantes.add(task);
         }
-        this.tachesRestantes.add(index, task);
     }
 
-    private Task getTask() {
-        return this.tachesRestantes.remove(0);
+    private Task getTask(Instance instance) {
+        if (priority == Priority.SPT || priority == Priority.LPT || priority == Priority.SRPT || priority == Priority.LRPT) {
+            return this.tachesRestantes.remove(0);
+        } else {
+            int indexBest = 0;
+            int indexChallenger;
+            for (indexChallenger = 1; indexChallenger < tachesRestantes.size(); indexChallenger++) {
+                if (prioritaire(instance, tachesRestantes.get(indexChallenger), tachesRestantes.get(indexBest))) {
+                    indexBest = indexChallenger;
+                }
+            }
+            return  this.tachesRestantes.remove(indexBest);
+        }
     }
 
     @Override
     public Result solve(Instance instance, long deadline) {
         //Initialisation
+        jobFreeDate = new int[instance.numJobs];
+        machineFreeDate = new int[instance.numMachines];
         int i;
         for (i=0; i<instance.numJobs; i++) {
-            try {
-                this.addTask(instance, new Task(i,0));
-            } catch (Exception e) {
-                System.out.println("ERREUR POLITIQUE DE PRIORITE INCONNUE");
-                System.exit(2);
-            }
+            this.addTask(instance, new Task(i,0));
+            this.jobFreeDate[i] = 0;
+        }
+        for (i=0; i<instance.numMachines; i++) {
+            this.machineFreeDate[i] = 0;
         }
         ResourceOrder resourceOrder = new ResourceOrder(instance);
         Task task;
@@ -117,16 +180,14 @@ public class GreedySolver implements Solver {
 
         //Itérations
         while (!this.tachesRestantes.isEmpty()) {
-            task = this.getTask();
+            task = this.getTask(instance);
+            int startTime = getEarliestDate(instance, task);
             resourceOrder.addTaskToMachine(instance.machine(task), task);
+            this.machineFreeDate[instance.machine(task)] = startTime + instance.duration(task);
+            this.jobFreeDate[task.job] = startTime + instance.duration(task);
             nextTask = instance.nextTask(task);
             if (nextTask != null) {
-                try {
-                    this.addTask(instance, new Task(task.job, task.task + 1));
-                } catch (Exception e) {
-                    System.out.println("ERREUR POLITIQUE DE PRIORITE INCONNUE");
-                    System.exit(2);
-                }
+                this.addTask(instance, new Task(task.job, task.task + 1));
             }
         }
         return new Result (instance, resourceOrder.toSchedule(), ProvedOptimal);
diff --git a/src/main/java/jobshop/solvers/Solver.java b/src/main/java/jobshop/solvers/Solver.java
index 462534c..0653031 100644
--- a/src/main/java/jobshop/solvers/Solver.java
+++ b/src/main/java/jobshop/solvers/Solver.java
@@ -2,6 +2,8 @@ package jobshop.solvers;
 
 import jobshop.Instance;
 import jobshop.Result;
+import jobshop.encodings.ResourceOrder;
+import jobshop.solvers.neighborhood.Nowicki;
 
 /** Common interface that must implemented by all solvers. */
 public interface Solver {
@@ -28,6 +30,14 @@ public interface Solver {
             case "est_lpt": return new GreedySolver(GreedySolver.Priority.EST_LPT);
             case "est_srpt": return new GreedySolver(GreedySolver.Priority.EST_SRPT);
             case "est_lrpt": return new GreedySolver(GreedySolver.Priority.EST_LRPT);
+            case "descent_spt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.SPT));
+            case "descent_lpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.LPT));
+            case "descent_srpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.SRPT));
+            case "descent_lrpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.LRPT));
+            case "descent_est_spt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.EST_SPT));
+            case "descent_est_lpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.EST_LPT));
+            case "descent_est_srpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.EST_SRPT));
+            case "descent_est_lrpt": return new DescentSolver(new Nowicki(), new GreedySolver(GreedySolver.Priority.EST_LRPT));
             // TODO: add new solvers
             default: throw new RuntimeException("Unknown solver: "+ name);
         }
diff --git a/src/main/java/jobshop/solvers/neighborhood/Nowicki.java b/src/main/java/jobshop/solvers/neighborhood/Nowicki.java
index 0d11f7e..f0d4636 100644
--- a/src/main/java/jobshop/solvers/neighborhood/Nowicki.java
+++ b/src/main/java/jobshop/solvers/neighborhood/Nowicki.java
@@ -1,8 +1,10 @@
 package jobshop.solvers.neighborhood;
 
 import jobshop.encodings.ResourceOrder;
+import jobshop.encodings.Task;
 
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
 /** Implementation of the Nowicki and Smutnicki neighborhood.
@@ -78,13 +80,13 @@ public class Nowicki extends Neighborhood<ResourceOrder> {
         /** Apply this swap on the given ResourceOrder, transforming it into a new solution. */
         @Override
         public void applyOn(ResourceOrder current) {
-            throw new UnsupportedOperationException();
+            current.swapTasks(machine, t1, t2);
         }
 
         /** Unapply this swap on the neighbor, transforming it back into the original solution. */
         @Override
         public void undoApplyOn(ResourceOrder current) {
-            throw new UnsupportedOperationException();
+            current.swapTasks(machine, t1, t2);
         }
     }
 
@@ -109,13 +111,50 @@ public class Nowicki extends Neighborhood<ResourceOrder> {
 
     /** Returns a list of all the blocks of the critical path. */
     List<Block> blocksOfCriticalPath(ResourceOrder order) {
-        throw new UnsupportedOperationException();
+        ArrayList<Block> results = new ArrayList<>();
+
+        List<Task> criticalPath = order.toSchedule().get().criticalPath();
+        int currentMachine = -1;
+        int currentFirstIndex = -1;
+        int currentLastIndex = -1;
+
+        Iterator<Task> iter = criticalPath.iterator();
+        Task currentTask;
+        if (iter.hasNext()) {
+            currentTask = iter.next();
+            currentMachine = order.instance.machine(currentTask);
+            currentFirstIndex = order.getIndexOfTaskOnMachine(currentMachine, currentTask);
+            currentLastIndex = currentFirstIndex;
+        }
+        while (iter.hasNext()) {
+            currentTask = iter.next();
+            if (currentMachine == order.instance.machine(currentTask)) {
+                currentLastIndex = order.getIndexOfTaskOnMachine(currentMachine, currentTask);
+            } else {
+                if (currentLastIndex > currentFirstIndex) {
+                    results.add(new Block(currentMachine, currentFirstIndex, currentLastIndex));
+                }
+                currentMachine = order.instance.machine(currentTask);
+                currentFirstIndex = order.getIndexOfTaskOnMachine(currentMachine, currentTask);
+                currentLastIndex = currentFirstIndex;
+            }
+        }
+        if (currentLastIndex > currentFirstIndex) {
+            results.add(new Block(currentMachine, currentFirstIndex, currentLastIndex));
+        }
+
+        return results;
     }
 
     /** For a given block, return the possible swaps for the Nowicki and Smutnicki neighborhood */
     List<Swap> neighbors(Block block) {
-        throw new UnsupportedOperationException();
-
+        ArrayList<Swap> swaps = new ArrayList<>();
+        if (block.lastTask - block.firstTask == 1) {
+            swaps.add(new Swap(block.machine, block.firstTask, block.lastTask));
+        } else {
+            swaps.add(new Swap(block.machine, block.firstTask, block.firstTask + 1));
+            swaps.add(new Swap(block.machine, block.lastTask - 1, block.lastTask));
+        }
+        return swaps;
     }
-
 }
diff --git a/src/test/java/jobshop/solvers/GreedySolverTest.java b/src/test/java/jobshop/solvers/GreedySolverTest.java
index 917f591..4075bc2 100644
--- a/src/test/java/jobshop/solvers/GreedySolverTest.java
+++ b/src/test/java/jobshop/solvers/GreedySolverTest.java
@@ -116,4 +116,121 @@ public class GreedySolverTest {
             }
         }
     }
+
+    @Test
+    public void testEST_SPT() {
+        List<String> instancesNames = BestKnownResults.instancesMatching("la");
+        instancesNames.addAll(BestKnownResults.instancesMatching("ft"));
+
+        List<Instance> instances = instancesNames.stream().map(name -> {
+            Instance instance = null;
+            try {
+                instance = Instance.fromFile(Paths.get("instances/", name));
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            return instance;
+        }).collect(Collectors.toList());
+
+        GreedySolver solver = new GreedySolver(EST_SPT);
+        Result result;
+        for (int i = 0; i < instances.size(); i++) {
+            result = solver.solve(instances.get(i), 100000);
+            assert result.schedule.get().isValid();
+            if (BestKnownResults.isKnown(instancesNames.get(i))) {
+                assert result.schedule.get().makespan() >= BestKnownResults.of(instancesNames.get(i));
+            }
+        }
+    }
+
+    @Test
+    public void testEST_LPT() throws IOException {
+        List<String> instancesNames = BestKnownResults.instancesMatching("la");
+        instancesNames.addAll(BestKnownResults.instancesMatching("ft"));
+
+        List<Instance> instances = instancesNames.stream().map(name -> {
+            Instance instance = null;
+            try {
+                instance = Instance.fromFile(Paths.get("instances/", name));
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            return instance;
+        }).collect(Collectors.toList());
+
+        GreedySolver solver = new GreedySolver(EST_LPT);
+        Result result;
+        for (int i = 0; i < instances.size(); i++) {
+            result = solver.solve(instances.get(i), 100000);
+            assert result.schedule.get().isValid();
+            if (BestKnownResults.isKnown(instancesNames.get(i))) {
+                assert result.schedule.get().makespan() >= BestKnownResults.of(instancesNames.get(i));
+            }
+        }
+    }
+
+    @Test
+    public void testEST_SRPT() throws IOException {
+        List<String> instancesNames = BestKnownResults.instancesMatching("la");
+        instancesNames.addAll(BestKnownResults.instancesMatching("ft"));
+
+        List<Instance> instances = instancesNames.stream().map(name -> {
+            Instance instance = null;
+            try {
+                instance = Instance.fromFile(Paths.get("instances/", name));
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            return instance;
+        }).collect(Collectors.toList());
+
+        GreedySolver solver = new GreedySolver(EST_SRPT);
+        Result result;
+        for (int i = 0; i < instances.size(); i++) {
+            result = solver.solve(instances.get(i), 100000);
+            assert result.schedule.get().isValid();
+            if (BestKnownResults.isKnown(instancesNames.get(i))) {
+                assert result.schedule.get().makespan() >= BestKnownResults.of(instancesNames.get(i));
+            }
+        }
+    }
+
+    @Test
+    public void testEST_LRPT() throws IOException {
+        List<String> instancesNames = BestKnownResults.instancesMatching("la");
+        instancesNames.addAll(BestKnownResults.instancesMatching("ft"));
+
+        List<Instance> instances = instancesNames.stream().map(name -> {
+            Instance instance = null;
+            try {
+                instance = Instance.fromFile(Paths.get("instances/", name));
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            return instance;
+        }).collect(Collectors.toList());
+
+        GreedySolver solver = new GreedySolver(EST_LRPT);
+        Result result;
+        for (int i = 0; i < instances.size(); i++) {
+            result = solver.solve(instances.get(i), 100000);
+            assert result.schedule.get().isValid();
+            if (BestKnownResults.isKnown(instancesNames.get(i))) {
+                assert result.schedule.get().makespan() >= BestKnownResults.of(instancesNames.get(i));
+            }
+        }
+    }
+
+    @Test
+    public void testSusucre() throws IOException {
+
+        Instance instance = Instance.fromFile(Paths.get("instances/aaa3"));
+
+        GreedySolver solver = new GreedySolver(EST_LRPT);
+        Result result = solver.solve(instance, 100000);
+        System.out.println("SCHEDULE EST_LRPT: " + result.schedule.get().toString());
+        solver = new GreedySolver(EST_SPT);
+        result = solver.solve(instance, 100000);
+        System.out.println("SCHEDULE EST_SPT: " + result.schedule.get().toString());
+    }
 }