2024/9/9 Hot100 回溯

src/main/java/com/cool/hot100/backtracking/Num46.java

@@ -0,0 +1,49 @@
+package com.cool.hot100.backtracking;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/09/14:39
+ * DayNumber 2
+ * Hard 2
+ * Level ?
+ */
+public class Num46 {
+
+
+    List<List<Integer>> resList = new ArrayList<>();
+    List<Integer> list = new ArrayList<>();
+
+    public List<List<Integer>> permute(int[] nums) {
+        for (int num : nums) {
+            list.add(num);
+        }
+        dfs(0);
+        return resList;
+    }
+
+    private void dfs(int x) {
+        if (x == list.size() - 1) {
+            resList.add(new ArrayList<>(list));
+            return;
+        }
+        for (int i = x; i < list.size(); i++) {
+            swap(i, x);
+            dfs(x + 1);
+            swap(i, x);
+        }
+    }
+
+    private void swap(int x, int y) {
+        int temp = list.get(x);
+        list.set(x, list.get(y));
+        list.set(y, temp);
+    }
+
+}

src/main/java/com/cool/hot100/backtracking/Num78.java

@@ -0,0 +1,38 @@
+package com.cool.hot100.backtracking;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/09/16:57
+ * DayNumber 3
+ * Hard 2
+ * Level ?
+ */
+public class Num78 {
+
+    List<List<Integer>> resList = new ArrayList<>();
+    List<Integer> list = new ArrayList<>();
+
+    public List<List<Integer>> subsets(int[] nums) {
+        dfs(nums, 0);
+        return resList;
+    }
+
+    private void dfs(int[] nums, int index) {
+        resList.add(new ArrayList<>(list));
+        if (index >= nums.length) {
+            return;
+        }
+        for (int i = index; i < nums.length; i++) {
+            list.add(nums[i]);
+            dfs(nums, i+1);
+            list.remove(list.size() - 1);
+        }
+
+    }
+
+}