backtracking started

Author: Subham1999

.idea/fileTemplates/internal/Class.java

@@ -28,4 +28,16 @@
             <version>3.1.8</version>
         </dependency>
     </dependencies>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>21</source>
+                    <target>21</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 </project>

.idea/inspectionProfiles/Project_Default.xml

@@ -0,0 +1,37 @@
+package com.subham.ta.backtracking;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CombinationSumI {
+  public List<List<Integer>> combinationSum(int[] candidates, int target) {
+    List<List<Integer>> result = new ArrayList<>();
+    List<Integer> runningSet = new ArrayList<>();
+    combinationSum(candidates, candidates.length - 1, target, result, runningSet);
+    return result;
+  }
+
+  void combinationSum(
+      int[] arr, int index, int target, List<List<Integer>> result, List<Integer> currentSet) {
+    if (index < 0 || target < 0) {
+      return;
+    }
+
+    if (target == 0) {
+      result.add(new ArrayList<>(currentSet));
+      return;
+    }
+
+    // include
+    currentSet.addLast(arr[index]);
+    combinationSum(arr, index, target - arr[index], result, currentSet);
+    currentSet.removeLast();
+
+    // exclude
+    combinationSum(arr, index - 1, target, result, currentSet);
+  }
+
+  public static void main(String[] args) {
+    System.out.println(new CombinationSumI().combinationSum(new int[] {2, 3, 6, 7}, 7));
+  }
+}

.idea/workspace.xml

@@ -0,0 +1,44 @@
+package com.subham.ta.backtracking;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * @author: Subham Santra
+ */
+public class PermutationI {
+
+  public List<List<Integer>> permute(int[] nums) {
+    List<List<Integer>> result = new ArrayList<>();
+    permute(nums, 0, result);
+    return result;
+  }
+
+  void permute(int[] arr, int i, List<List<Integer>> result) {
+    if (i == arr.length) {
+      result.add(Arrays.stream(arr).boxed().collect(Collectors.toList()));
+      return;
+    }
+
+    for (int j = i; j < arr.length; ++j) {
+      swap(arr, i, j);
+      permute(arr, i + 1, result);
+      swap(arr, i, j);
+    }
+  }
+
+  void swap(int[] arr, int f, int t) {
+    int x = arr[f];
+    arr[f] = arr[t];
+    arr[t] = x;
+  }
+
+  public static void main(String[] args) {
+    System.out.println(new PermutationI().permute(new int[] {0}));
+    System.out.println(new PermutationI().permute(new int[] {1}));
+    System.out.println(new PermutationI().permute(new int[] {1, 2}));
+    System.out.println(new PermutationI().permute(new int[] {1, 2, 3}));
+  }
+}