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Update the code of permutations I and II

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krahets
2023-04-27 01:29:00 +08:00
parent 3f430fb85e
commit 9c070a028f
3 changed files with 72 additions and 22 deletions
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27
codes/csharp/chapter_backtracking/permutations_i.cs
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@ -7,11 +7,11 @@
using hello_algo.utils;
using NUnit.Framework;
namespace hello_algo.chapter_backtracking;
namespace hello_algo.chapter_backtracking;
public class permutations_i {
/* 回溯算法：全排列 I */
public static void backtrack(List<int> state, int[] choices, bool[] selected, List<List<int>> res) {
static void backtrack(List<int> state, int[] choices, bool[] selected, List<List<int>> res) {
// 当状态长度等于元素数量时，记录解
if (state.Count == choices.Length) {
res.Add(new List<int>(state));
@ -22,24 +22,29 @@ 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.RemoveAt(state.Count - 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.RemoveAt(state.Count - 1);
}
}
}
/* 全排列 I */
static List<List<int>> permutationsI(int[] nums) {
List<List<int>> res = new List<List<int>>();
backtrack(new List<int>(), nums, new bool[nums.Length], res);
return res;
}
[Test]
public void Test() {
int[] nums = { 1, 2, 3 };
// 回溯算法
List<List<int>> res = new List<List<int>>();
backtrack(new List<int>(), nums, new bool[nums.Length], res);
List<List<int>> res = permutationsI(nums);
Console.WriteLine("输入数组 nums = " + string.Join(", ", nums));
Console.WriteLine("所有排列 res = ");