LeetCode Permutations

Given a collection of numbers, return all possible permutations.

For example,

[1,2,3]

 have the following permutations:

[1,2,3]

, 

[1,3,2]

, 

[2,1,3]

, 

[2,3,1]

, 

[3,1,2]

,
and 

[3,2,1]

.

class Solution {
public:
vector<vector<int> > permute(vector<int> &num) {
vector<vector<int> > ivecArray;
if (num.size() == 0)
return ivecArray;
recursive(ivecArray, num, 0);
return ivecArray;
}

void recursive(vector<vector<int> > &ivecArray, vector<int> &num, int start) {
int n = num.size();
if (start == n) {
ivecArray.push_back(num);
return;
}
for (int i = start; i < n; i++) {
swap(num[i], num[start]);
recursive(ivecArray, num, start + 1);
swap(num[i], num[start]);
}
}
};

使用STL库函数
class Solution {
public:
vector<vector<int> > permute(vector<int> &num) {
vector<vector<int> > ivecArray;
if (num.size() == 0)
return ivecArray;
sort(num.begin(), num.end());
ivecArray.push_back(num);
while (next_permutation(num.begin(), num.end())) {
ivecArray.push_back(num);
}
return ivecArray;
}
};