题目连接：Leetcode 046 Permutations
解题思路：用 Leetcode 031的方法，每次获取下一个序列。
class Solution {
public:
bool nextPermutation(vector<int>& nums) {
int n = nums.size();
int idx = n - 1;
while (idx && nums[idx-1] >= nums[idx]) idx--;
if (idx) {
int p = n - 1;
while (p >= idx && nums[p] <= nums[idx-1]) p--;
int tmp = nums[idx-1];
nums[idx-1] = nums[p];
nums[p] = tmp;
sort(nums.begin() + idx, nums.end());
return true;
} else {
sort(nums.begin(), nums.end());
return false;
}
}
vector<vector<int>> permute(vector<int>& nums) {
vector<vector<int>> ans;
sort(nums.begin(), nums.end());
ans.push_back(nums);
while (nextPermutation(nums)) ans.push_back(nums);
return ans;
}
};
