Leetcode#31 Next Permutation

class Solution {
    public:
        void nextPermutation(vector<int>& nums) {
            if (nums.size() <= 1)
                return;

            int i=nums.size()-1;

            /* From right to left, find the first digit(partitionNumber) which violates the increase trend */
            while(i>0) {
                if (nums[i] <= nums[i-1]) {
                    i--;
                } else {
                    break;
                }
            }

            cout<<i<<endl;
            /* If not found, it means the current sequence is already the largest permutation */
            if(i==0) {
                reverse(nums, 0, nums.size()-1);
                return;
            }

            /* From right to left, find the first digit which is greater than the partition number, call it changeNumber */
            for(int j=nums.size()-1; j>=i; j--) {
                if(nums[j]>nums[i-1]) {
                    /* swap */
                    int tmp = nums[i-1];
                    nums[i-1] = nums[j];
                    nums[j] = tmp;
                    break;
                }
            }

            /* Reverse all digits  on the right of partitionNumber */
            reverse(nums, i, nums.size()-1);
            return;
        }

        void reverse(vector<int>& nums, int begin, int end) {
            while(end >= begin) {
                int tmp = nums[end];
                nums[end] = nums[begin];
                nums[begin] = tmp;
                begin++;
                end--;
            }
        }
};