Next Permutation

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本文介绍了一个用于重新排列数字数组以获得下一个更大排列的算法。如果无法实现，则将其排列为最小可能顺序。该方法实现了就地操作，无需额外内存。

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

#include<iostream>
#include<vector>
#include<algorithm>
#include<iterator>
#include<ostream>
using namespace std;

void nextPermutation(vector<int> &num) {

	vector<int>::reverse_iterator pre_iter;
	for (pre_iter = num.rbegin()+1;pre_iter!=num.rend();++pre_iter){
		vector<int>::reverse_iterator tmp_iter =pre_iter;
		advance(tmp_iter,-1);
		if (*pre_iter<*tmp_iter)
			break;
	}
	if (pre_iter==num.rend()){
		reverse(num.begin(),num.end());
		return;
	}
	vector<int>::reverse_iterator las_iterator;
	for (las_iterator = num.rbegin();las_iterator!=pre_iter;++las_iterator){
		if (*las_iterator>*pre_iter)
			break;
	}
	iter_swap(pre_iter,las_iterator);
	reverse((pre_iter++).base(),num.end());
}