递归实现：

class Solution {public:    /**     * @param nums: A list of integers.     * @return: A list of permutations.     */    vector
     
      
        > permute(vector
       
         nums) {        // write your code here        vector
        
         
           > permutations;        if (nums.empty()) return permutations;        permutate(nums, 0, permutations);        return permutations;    }private:    void permutate(vector
          
            nums, int start, vector
           
            
              >& permutations) { if (start == nums.size()) { permutations.push_back(nums); return; } for (int i = start; i < (int)nums.size(); i++) { swap(nums[start], nums[i]); permutate(nums, start + 1, permutations); } }};
            
           
          
         
        
       
      
     

非递归实现（基于nextPermutation）：

1 class Solution { 2 public: 3     /** 4      * @param nums: A list of integers. 5      * @return: A list of permutations. 6      */ 7     vector
     
      
        > permute(vector
       
         nums) { 8         // write your code here 9         vector
        
         
           > permutations;10         if (nums.empty()) return permutations;11         vector
          
            copy(nums.begin(), nums.end());12 nextPermutation(nums);13 permutations.push_back(nums);14 while (nums != copy) {15 nextPermutation(nums);16 permutations.push_back(nums);17 }18 return permutations;19 }20 private:21 void nextPermutation(vector
           
            & nums) {22 int k = -1, n = nums.size();23 for (int i = n - 2; i >= 0; i--) {24 if (nums[i] < nums[i + 1]) {25 k = i;26 break;27 }28 }29 if (k == -1) {30 reverse(nums.begin(), nums.end());31 return;32 }33 int l;34 for (int i = n - 1; i > k; i--) {35 if (nums[i] > nums[k]) {36 l = i;37 break;38 }39 }40 swap(nums[l], nums[k]);41 reverse(nums.begin() + k + 1, nums.end());42 }43 };