LeetCode: Next Permutation

思路还是清楚的，从后面倒着数，中间有一些问题没考虑到，不过很快解决，少数次过

class Solution {
public:
    void nextPermutation(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> des;
        int i;
        for (i = num.size()-1; i > 0; i--) {
            if (num[i] <= num[i-1]) des.push_back(num[i]);
            else break;
        }
        if (!i) {
            des.push_back(num[0]);
            num = des;
        }
        else {
            int tmp = num[i-1];
            des.push_back(num[i]);
            int j;
            for (j = 0; j < des.size(); j++) 
                if (des[j] > num[i-1]) break;
            num[i-1] = des[j];
            for (int k = 0; k < des.size(); k++) {
                if (k != j) num[i+k] = des[k];
                else num[i+k] = tmp;
            } 
        }
    }
};

 后来写了段更加好的代码

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

 C#, Array.Reverse()函数并不能对一段Array进行Reverse，所以没选择第二段代码

public class Solution {
    public void NextPermutation(int[] nums) {
        List<int> des = new List<int>();
        int i = 0;
        for (i = nums.Length-1; i > 0; i--) {
            if (nums[i] <= nums[i-1]) des.Add(nums[i]);
            else break;
        }
        if (i == 0) {
            des.Add(nums[0]);
            for (int k = 0; k < des.Count; k++) nums[k] = des[k];
        }
        else {
            int tmp = nums[i-1];
            des.Add(nums[i]);
            int j = 0;
            for (j = 0; j < des.Count; j++) {
                if (des[j] > nums[i-1]) break;
            }
            nums[i-1] = des[j];
            for (int k = 0; k < des.Count; k++) {
                if (k != j) nums[i+k] = des[k];
                else nums[i+k] = tmp;
            }
        }
    }
}