给定一个没有重复数字的序列,返回其所有可能的全排列。
示例:
输入: [1,2,3]
输出:
[
[1,2,3],
[1,3,2],
[2,1,3],
[2,3,1],
[3,1,2],
[3,2,1]
]
解题思路:这个...感觉很难讲明白,大家看代码自己体会吧......
java代码:
class Solution {
public List<List<Integer>> permute(int[] nums) {
List<List<Integer>> result = new LinkedList<>();
int[] flag = new int[nums.length];
List<Integer> innerLS = new ArrayList<>(nums.length);
helper(nums, flag, nums.length, innerLS, result);
return result;
}
void helper(int[] nums, int[] flag, int leftCnt, List<Integer> innerLS, List<List<Integer>> outerLS){
if(0 == leftCnt){
outerLS.add(innerLS);
return;
}
for(int index = 0; index < nums.length; index++){
if(0 == flag[index]){
int[] f = Arrays.copyOf(flag, flag.length);
List<Integer> i = new ArrayList<>(innerLS);
int left = leftCnt;
f[index] = 1;
i.add(nums[index]);
helper(nums, f, --left, i, outerLS);
}
}
}
}