Update the code of permutations i and ii

codes/c/utils/list_node.h

@@ -3,6 +3,7 @@
  * Created Time: 2023-01-09
  * Author: Reanon (793584285@qq.com)
  */
+
 #ifndef LIST_NODE_H
 #define LIST_NODE_H
 

codes/cpp/chapter_backtracking/permutations_i.cpp

@@ -18,26 +18,31 @@ void backtrack(vector<int> &state, const vector<int> &choices, vector<bool> &sel
         int choice = choices[i];
         // 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
         if (!selected[i]) {
-            // 尝试
-            selected[i] = true;      // 做出选择
-            state.push_back(choice); // 更新状态
+            // 尝试：做出选择，更新状态
+            selected[i] = true;
+            state.push_back(choice);
             backtrack(state, choices, selected, res);
-            // 回退
-            selected[i] = false; // 撤销选择
-            state.pop_back();    // 恢复到之前的状态
+            // 回退：撤销选择，恢复到之前的状态
+            selected[i] = false;
+            state.pop_back();
         }
     }
 }
 
+/* 全排列 I */
+vector<vector<int>> permutationsI(vector<int> nums) {
+    vector<int> state;
+    vector<bool> selected(nums.size(), false);
+    vector<vector<int>> res;
+    backtrack(state, nums, selected, res);
+    return res;
+}
+
 /* Driver Code */
 int main() {
     vector<int> nums = {1, 2, 3};
 
-    // 回溯算法
-    vector<int> state;
-    vector<bool> selected(nums.size(), false);
-    vector<vector<int>> res;
-    backtrack(state, nums, selected, res);
+    vector<vector<int>> res = permutationsI(nums);
 
     cout << "输入数组 nums = ";
     printVector(nums);

codes/cpp/chapter_backtracking/permutations_ii.cpp

@@ -19,27 +19,32 @@ void backtrack(vector<int> &state, const vector<int> &choices, vector<bool> &sel
         int choice = choices[i];
         // 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
         if (!selected[i] && duplicated.find(choice) == duplicated.end()) {
-            // 尝试
+            // 尝试：做出选择，更新状态
             duplicated.emplace(choice); // 记录选择过的元素值
-            selected[i] = true;         // 做出选择
-            state.push_back(choice);    // 更新状态
+            selected[i] = true;
+            state.push_back(choice);
             backtrack(state, choices, selected, res);
-            // 回退
-            selected[i] = false; // 撤销选择
-            state.pop_back();    // 恢复到之前的状态
+            // 回退：撤销选择，恢复到之前的状态
+            selected[i] = false;
+            state.pop_back();
         }
     }
 }
 
+/* 全排列 II */
+vector<vector<int>> permutationsII(vector<int> nums) {
+    vector<int> state;
+    vector<bool> selected(nums.size(), false);
+    vector<vector<int>> res;
+    backtrack(state, nums, selected, res);
+    return res;
+}
+
 /* Driver Code */
 int main() {
     vector<int> nums = {1, 1, 2};
 
-    // 回溯算法
-    vector<int> state;
-    vector<bool> selected(nums.size(), false);
-    vector<vector<int>> res;
-    backtrack(state, nums, selected, res);
+    vector<vector<int>> res = permutationsII(nums);
 
     cout << "输入数组 nums = ";
     printVector(nums);

codes/java/chapter_backtracking/permutations_i.java

@@ -21,23 +21,28 @@ public class permutations_i {
             int choice = choices[i];
             // 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
             if (!selected[i]) {
-                // 尝试
-                selected[i] = true; // 做出选择
-                state.add(choice); // 更新状态
+                // 尝试：做出选择，更新状态
+                selected[i] = true;
+                state.add(choice);
                 backtrack(state, choices, selected, res);
-                // 回退
-                selected[i] = false; // 撤销选择
-                state.remove(state.size() - 1); // 恢复到之前的状态
+                // 回退：撤销选择，恢复到之前的状态
+                selected[i] = false;
+                state.remove(state.size() - 1);
             }
         }
     }
 
+    /* 全排列 I */
+    static List<List<Integer>> permutationsI(int[] nums) {
+        List<List<Integer>> res = new ArrayList<List<Integer>>();
+        backtrack(new ArrayList<Integer>(), nums, new boolean[nums.length], res);
+        return res;
+    }
+
     public static void main(String[] args) {
         int[] nums = { 1, 2, 3 };
-        List<List<Integer>> res = new ArrayList<List<Integer>>();
 
-        // 回溯算法
-        backtrack(new ArrayList<Integer>(), nums, new boolean[nums.length], res);
+        List<List<Integer>> res = permutationsI(nums);
 
         System.out.println("输入数组 nums = " + Arrays.toString(nums));
         System.out.println("所有排列 res = " + res);

codes/java/chapter_backtracking/permutations_ii.java

@@ -10,7 +10,7 @@ import java.util.*;
 
 public class permutations_ii {
     /* 回溯算法：全排列 II */
-    public static void backtrack(List<Integer> state, int[] choices, boolean[] selected, List<List<Integer>> res) {
+    static void backtrack(List<Integer> state, int[] choices, boolean[] selected, List<List<Integer>> res) {
         // 当状态长度等于元素数量时，记录解
         if (state.size() == choices.length) {
             res.add(new ArrayList<Integer>(state));
@@ -22,24 +22,29 @@ public class permutations_ii {
             int choice = choices[i];
             // 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
             if (!selected[i] && !duplicated.contains(choice)) {
-                // 尝试
+                // 尝试：做出选择，更新状态
                 duplicated.add(choice); // 记录选择过的元素值
-                selected[i] = true; // 做出选择
-                state.add(choice); // 更新状态
+                selected[i] = true;
+                state.add(choice);
                 backtrack(state, choices, selected, res);
-                // 回退
-                selected[i] = false; // 撤销选择
-                state.remove(state.size() - 1); // 恢复到之前的状态
+                // 回退：撤销选择，恢复到之前的状态
+                selected[i] = false;
+                state.remove(state.size() - 1);
             }
         }
     }
 
+    /* 全排列 II */
+    static List<List<Integer>> permutationsII(int[] nums) {
+        List<List<Integer>> res = new ArrayList<List<Integer>>();
+        backtrack(new ArrayList<Integer>(), nums, new boolean[nums.length], res);
+        return res;
+    }
+
     public static void main(String[] args) {
         int[] nums = { 1, 2, 2 };
-        List<List<Integer>> res = new ArrayList<List<Integer>>();
 
-        // 回溯算法
-        backtrack(new ArrayList<Integer>(), nums, new boolean[nums.length], res);
+        List<List<Integer>> res = permutationsII(nums);
 
         System.out.println("输入数组 nums = " + Arrays.toString(nums));
         System.out.println("所有排列 res = " + res);

codes/python/chapter_backtracking/permutations_i.py

@@ -22,22 +22,27 @@ def backtrack(
     for i, choice in enumerate(choices):
         # 剪枝：不允许重复选择元素
         if not selected[i]:
-            # 尝试
-            selected[i] = True  # 做出选择
-            state.append(choice)  # 更新状态
+            # 尝试：做出选择，更新状态
+            selected[i] = True
+            state.append(choice)
             backtrack(state, choices, selected, res)
-            # 回退
-            selected[i] = False  # 撤销选择
-            state.pop()  # 恢复到之前的状态
+            # 回退：撤销选择，恢复到之前的状态
+            selected[i] = False
+            state.pop()
+
+
+def permutations_i(nums: list[int]) -> list[list[int]]:
+    """全排列 I"""
+    res = []
+    backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
+    return res
 
 
 """Driver Code"""
 if __name__ == "__main__":
     nums = [1, 2, 3]
-    res = []
 
-    # 回溯算法
-    backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
+    res = permutations_i(nums)
 
     print(f"输入数组 nums = {nums}")
     print(f"所有排列 res = {res}")

codes/python/chapter_backtracking/permutations_ii.py

@@ -23,23 +23,28 @@ def backtrack(
     for i, choice in enumerate(choices):
         # 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
         if not selected[i] and choice not in duplicated:
-            # 尝试
+            # 尝试：做出选择，更新状态
             duplicated.add(choice)  # 记录选择过的元素值
-            selected[i] = True  # 做出选择
-            state.append(choice)  # 更新状态
+            selected[i] = True
+            state.append(choice)
             backtrack(state, choices, selected, res)
-            # 回退
-            selected[i] = False  # 撤销选择
-            state.pop()  # 恢复到之前的状态
+            # 回退：撤销选择，恢复到之前的状态
+            selected[i] = False
+            state.pop()
+
+
+def permutations_ii(nums: list[int]) -> list[list[int]]:
+    """全排列 II"""
+    res = []
+    backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
+    return res
 
 
 """Driver Code"""
 if __name__ == "__main__":
     nums = [1, 2, 2]
-    res = []
 
-    # 回溯算法
-    backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
+    res = permutations_ii(nums)
 
     print(f"输入数组 nums = {nums}")
     print(f"所有排列 res = {res}")