LeetCode 3 Longest Substring Without Repeating Characters

Problem:

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.

Solution:

无

题目大意：

题意比较简单，给定一个字符串，要求得出最长子串的长度，子串要求无重复字符。

解题思路：

可以采用Hash存储+动态规划的方式解决，从左到右遍历一遍，标记子串的最左边位置，当遇到重复字符时，说明当前子串已经结束，开始一个新的字符串，更新字符的位置和子串的left。

Java源代码：

public class Solution {    public int lengthOfLongestSubstring(String s) {        int left=0,Max=0;        Map<Character,Integer> map = new HashMap<Character,Integer>();        char[] chs = s.toCharArray();        for(int i=0;i<chs.length;i++){            if(map.containsKey(chs[i]) && map.get(chs[i])>=left){                left = map.get(chs[i])+1;            }            map.put(chs[i],i);            Max = Max>(i-left+1)?Max:(i-left+1);        }        return Max;    }}

C语言源代码：

#include<limits.h>#include<stdio.h>int lengthOfLongestSubstring(char* s) {    int i,j,left=0,Max=0,hash[256];    for(j=0;j<256;j++)hash[j]=INT_MAX;    for(i=0;s[i];i++){        if(hash[s[i]]!=INT_MAX && hash[s[i]]>=left)            left=hash[s[i]]+1;        hash[s[i]]=i;        Max = Max>(i-left+1)?Max:(i-left+1);    }    return Max;}

C++源代码：

class Solution {public:    int lengthOfLongestSubstring(string s) {        int Max=0,left=0;        map<int,int> map;        for(int i=0;i<s.size();i++){            std::map<int,int>::iterator iter=map.find(s[i]);            if(iter!=map.end() && iter->second >=left){                left=iter->second+1;            }            map[s[i]]=i;            Max = Max>(i-left+1)?Max:(i-left+1);        }        return Max;    }};

Python源代码：

class Solution:    # @param {string} s    # @return {integer}    def lengthOfLongestSubstring(self, s):        left=0        Max=0        hash={}        for i in range(len(s)):            ch = s[i]            if hash.has_key(ch) and hash[ch]>=left:                left=hash[ch]+1            hash[ch]=i            Max= Max if Max>i-left+1 else i-left+1        return Max