55 lines
1.3 KiB
C++
55 lines
1.3 KiB
C++
/**
|
|
* File: permutations_i.cpp
|
|
* Created Time: 2023-04-24
|
|
* Author: krahets (krahets@163.com)
|
|
*/
|
|
|
|
#include "../utils/common.hpp"
|
|
|
|
/* 回溯算法：全排列 I */
|
|
void backtrack(vector<int> &state, const vector<int> &choices, vector<bool> &selected, vector<vector<int>> &res) {
|
|
// 当状态长度等于元素数量时，记录解
|
|
if (state.size() == choices.size()) {
|
|
res.push_back(state);
|
|
return;
|
|
}
|
|
// 遍历所有选择
|
|
for (int i = 0; i < choices.size(); i++) {
|
|
int choice = choices[i];
|
|
// 剪枝：不允许重复选择元素
|
|
if (!selected[i]) {
|
|
// 尝试：做出选择，更新状态
|
|
selected[i] = true;
|
|
state.push_back(choice);
|
|
// 进行下一轮选择
|
|
backtrack(state, choices, selected, res);
|
|
// 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};
|
|
|
|
vector<vector<int>> res = permutationsI(nums);
|
|
|
|
cout << "输入数组 nums = ";
|
|
printVector(nums);
|
|
cout << "所有排列 res = ";
|
|
printVectorMatrix(res);
|
|
|
|
return 0;
|
|
}
|