[LeetCode] 31. Next Permutation 下一个排列

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

The replacement must be in-place and use only constant extra memory.

Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.

1,2,3 → 1,3,2
3,2,1 → 1,2,3
1,1,5 → 1,5,1

1　　2　　7　　4　　3　　1

1　　3　　1　　2　　4　　7

1　　2　　7　　4　　3　　1

1　　2　　7　　4　　3　　1

1　　3　　7　　4　　2　　1

1　　3　　1　　2　　4　　7

class Solution {
public:
void nextPermutation(vector<int> &num) {
int i, j, n = num.size();
for (i = n - 2; i >= 0; --i) {
if (num[i + 1] > num[i]) {
for (j = n - 1; j > i; --j) {
if (num[j] > num[i]) break;
}
swap(num[i], num[j]);
reverse(num.begin() + i + 1, num.end());
return;
}
}
reverse(num.begin(), num.end());
}
};

class Solution {
public:
void nextPermutation(vector<int>& nums) {int n = nums.size(), i = n - 2, j = n - 1;
while (i >= 0 && nums[i] >= nums[i + 1]) --i;
if (i >= 0) {
while (nums[j] <= nums[i]) --j;
swap(nums[i], nums[j]);
}
reverse(nums.begin() + i + 1, nums.end());
}
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/31

Permutations II

Permutations

Permutation Sequence

Palindrome Permutation

https://leetcode.com/problems/next-permutation/

https://leetcode.com/problems/next-permutation/discuss/13921/1-4-11-lines-C%2B%2B

https://leetcode.com/problems/next-permutation/discuss/13867/C%2B%2B-from-Wikipedia

LeetCode All in One 题目讲解汇总(持续更新中...)

posted @ 2015-04-15 12:53  Grandyang  阅读(42161)  评论(13编辑  收藏  举报