Next Permutation

void nextPermutation(vector<int> &num) {
    // Start typing your C/C++ solution below
    // DO NOT write int main() function
    vector<int>::iterator it = num.end() - 1;

    while (it!=num.begin() && (*(it-1) >= *it)) it--; //find *(it-1) < *it
    if (it == num.begin()) { //last element, rewind to the first one, i.e, ascending order
        reverse(it, num.end());
        return;
    }
    it--; //left elem to be exchanged

    vector<int>::iterator rit = it+1;
    while (rit!=num.end() && *rit > *it) rit++;
    rit--; //right elem to be exchanged

    //swap (left,right), then reverse right part to ascending order
    iter_swap(it, rit);
    reverse(it+1, num.end());
}

class Solution {
public:
    void nextPermutation(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        for (int i = num.size() - 2; i >= 0; --i) {
            if (num[i] < num[i + 1]) {
                for (int j = i + 1; j < num.size(); ++j) {
                    if (j == num.size() - 1 || num[j + 1] <= num[i]) {
                        swap(num[i], num[j]);
                        reverse(num.begin() + i + 1, num.end());
                        return;
                    }
                }
            }
        }
        reverse(num.begin(), num.end());
    }
};

public void nextPermutation(int[] num) {

    for(int i = num.length - 1; i >= 0; i--) {
        for(int j = i - 1; j >= 0; j--) {
            if(num[j] < num[i]) {
                // find the first num[j] < num[i], swap them, and sort elements after j
                int temp = num[j];
                num[j] = num[i];
                num[i] = temp;

                Arrays.sort(num, j + 1, num.length);
                return;
            }
        }
    }

    Arrays.sort(num);
}