zoukankan      html  css  js  c++  java
  • Leetcode: 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.

    Example

    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
    

    思路

    • 从前往后找到最后一组前面数比后面数大的,这两个数不一定相邻
    • 然后交换
    • 交换完了之后,从交换完后的第一个数后面开始排序
    • STL里面有个next_permutation(list, list)一步到位。。
      bool next_permutation( iterator start, iterator end);
      

    代码

    class Solution {
    public:
        void nextPermutation(vector<int>& nums) {
            int len = nums.size();
            if(len <= 1) return;
            
            int index1 = -1, index2 = -1, min_flag = -1;
            for(int i = 1; i < len; ++i){
                if(nums[i] == nums[i - 1]) continue;
                else if(nums[i] > nums[i - 1]){
                    index1 = i - 1;
                    index2 = i;
                    min_flag = nums[i] - nums[i - 1];
                }
                else if(index1 != -1 && nums[i] > nums[index1] && nums[i] - nums[index1] <= min_flag ){
                    index2 = i;
                    min_flag = nums[i] - nums[index1];
                }
            }
            
            if(index1 != -1 && index2 != -1){
                swap(nums[index1], nums[index2]);
                sort(nums.begin() + index1 + 1, nums.end());
            }
            else sort(nums.begin(), nums.end());
        }
    };
    
  • 相关阅读:
    队列的定义与实现(C语言实现)
    在CTime类中重载&lt;&lt;和&gt;&gt;
    华为OJ:统计大写字母个数
    sql server smo
    应用服务器负载平衡集群
    存储过程如何执行的快速
    sql server 分布式事务
    代理服务器
    怎样实现数据库负载均衡集群
    多层插件开发框架
  • 原文地址:https://www.cnblogs.com/lengender-12/p/6834675.html
Copyright © 2011-2022 走看看