zoukankan      html  css  js  c++  java
  • 【leetcode刷题笔记】Longest Substring Without Repeating Characters

    Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.


    题解:贪心算法。

    利用一个hashmap存放当前最长的无重substring所包含的元素,变量leftbound存放当前的最左边界。则当前遍历的字符s[i]有两种情况:

    1. s[i]所指的元素已经存在在map中了,那么就左移leftbound直到leftbound到i这一段不再包含s[i],并且在map中清除leftbound扫过的元素;
    2. s[i]所指的元素不在map中,保持leftbound不动,查看是否需要更新当前最长substring的长度。

    代码如下:

     1 public class Solution {
     2     public int lengthOfLongestSubstring(String s) {
     3         if(s == null || s.length() == 0)
     4             return 0;
     5             
     6         HashMap<Character, Integer> map = new HashMap<Character, Integer>();
     7         int leftebound = 0;
     8         int answer = 0;
     9        
    10         for(int i = 0;i < s.length();i++){
    11             char current = s.charAt(i);
    12             if(map.containsKey(s.charAt(i))){                
    13                 while(s.charAt(leftebound) != current && leftebound < i){
    14                     map.remove(s.charAt(leftebound));
    15                     leftebound++;
    16                 }
    17                 leftebound++;
    18             }
    19             else {
    20                 map.put(current, 0);
    21                 answer = Math.max(i-leftebound+1, answer);
    22             }
    23         }
    24         
    25         return answer;    
    26     }
    27 }       
  • 相关阅读:
    Android 画布绘图
    Android 4.2.2原生Launcher修改使之可以运行过程小结
    canvas的translate、scale、rotate等方法
    WorkSpace介绍
    Libgdx New 3D API 教程之 -- 加载3D场景的背后-第二部分
    Libgdx New 3D API 教程之 -- 使用Libgdx加载模型
    LibGdx----Texture, TextureRegion, SpriteBatch
    libgdx学习之Camera
    Java伪代码
    读大道至简之感
  • 原文地址:https://www.cnblogs.com/sunshineatnoon/p/3863134.html
Copyright © 2011-2022 走看看