2018.1.13 LeetCode 31. Next Permutation 46. Permutations【STL -> 全排列】

31. Next Permutation

Description

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, do not allocate 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

题意： 求下一个排列，如果没有的话，返回最小的排列

分析： 直接STL里的 std::next_permutation(begin(),end()),即可

参考函数

class Solution {
public:
void nextPermutation(vector<int>& nums) {
if(!next_permutation(nums.begin(),nums.end())) {
sort(nums.begin(),nums.end());
}
}
};

46. Permutations

Description

Given a collection of distinct numbers, return all possible permutations.

For example,

[1,2,3] have the following permutations:

[

[1,2,3],

[1,3,2],

[2,1,3],

[2,3,1],

[3,1,2],

[3,2,1]

]

题意： 求全排列

分析 ： 同上

参考函数

class Solution {
public:
vector<vector<int>> permute(vector<int>& nums) {
vector<vector<int> > res;
sort(nums.begin(),nums.end());
res.push_back(nums);
while (next_permutation(nums.begin(),nums.end())) {
res.push_back(nums);
}
return res;
}
};