力扣46题——全排列 https://leetcode-cn.com/problems/permutations/submissions/
swap() 使用加减法交换两个数,为什么用加减法交换数组中两个位置的数组,结果集合中全为0,求解答。
class Solution {
List<List<Integer>> res = new ArrayList<>();
public List<List<Integer>> permute(int[] nums) {
permuteHelper(nums, 0);
return res;
}
void permuteHelper(int[] nums, int k) {
if (k == nums.length) {
List<Integer> temp = new ArrayList<>();
for (int i = 0; i < nums.length; i++) {
temp.add(nums[i]);
}
res.add(temp);
}
for (int i = k; i < nums.length; i++) {
swap(nums, i, k);
permuteHelper(nums, k + 1);
swap(nums, i, k);
}
}
void swap(int[] nums, int i, int j) {
nums[i] = nums[i] + nums[j];
nums[j] = nums[i] - nums[j];
nums[i] = nums[i] - nums[j];
}
}
输出: [[0,0,0],[0,0,0],[0,0,0],[0,0,0],[0,0,0],[0,0,0]]
使用临时变量就可以~
void swap(int[] nums, int i, int j) {
int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
输出:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,2,1],[3,1,2]]