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

 1 class Solution {

 2 public:

 3     void nextPermutation(vector<int> &num) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         vector<int> des;

 7         int i;

 8         for (i = num.size()-1; i > 0; i--) {

 9             if (num[i] <= num[i-1]) des.push_back(num[i]);

10             else break;

11         }

12         if (!i) {

13             des.push_back(num[0]);

14             num = des;

15         }

16         else {

17             int tmp = num[i-1];

18             des.push_back(num[i]);

19             int j;

20             for (j = 0; j < des.size(); j++) 

21                 if (des[j] > num[i-1]) break;

22             num[i-1] = des[j];

23             for (int k = 0; k < des.size(); k++) {

24                 if (k != j) num[i+k] = des[k];

25                 else num[i+k] = tmp;

26             } 

27         }

28     }

29 };

 后来写了段更加好的代码

 1 class Solution {

 2 public:

 3     void nextPermutation(vector<int> &num) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         if (!num.size()) return;

 7         int pos = num.size();

 8         for (int i = num.size()-1; i >= 0; i--) {

 9             if (i && num[i] > num[i-1]) {

10                 pos = i;

11                 break;

12             }

13         }

14         if (pos == num.size()) {

15             reverse(num.begin(), num.end());

16             return;

17         }

18         for (int i = num.size()-1; i >= pos; i--) {

19             if (num[i] > num[pos-1]) {

20                 swap(num[i], num[pos-1]);

21                 break;

22             }

23         }

24         reverse(num.begin()+pos, num.end());

25     }

26 };

 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

 1 public class Solution {

 2     public void NextPermutation(int[] nums) {

 3         List<int> des = new List<int>();

 4         int i = 0;

 5         for (i = nums.Length-1; i > 0; i--) {

 6             if (nums[i] <= nums[i-1]) des.Add(nums[i]);

 7             else break;

 8         }

 9         if (i == 0) {

10             des.Add(nums[0]);

11             for (int k = 0; k < des.Count; k++) nums[k] = des[k];

12         }

13         else {

14             int tmp = nums[i-1];

15             des.Add(nums[i]);

16             int j = 0;

17             for (j = 0; j < des.Count; j++) {

18                 if (des[j] > nums[i-1]) break;

19             }

20             nums[i-1] = des[j];

21             for (int k = 0; k < des.Count; k++) {

22                 if (k != j) nums[i+k] = des[k];

23                 else nums[i+k] = tmp;

24             }

25         }

26     }

27 }

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