最长字符串

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define MAX(a ,b) ((a)<(b)? (b):(a))

int lengthOfLongestSubstring2(char * s)
{
    int hash[127] = {0};

    int left = 0,right = 0,max =0;

    while(s[right])
    {
        if (hash[s[right]] && (left < hash[s[right]]))
        {
            left = hash[s[right]] ;
        }
        
        hash[s[right]] = right + 1;
        max = MAX(max,(right - left +1));
        right++;
    }
    return max;
}

int lengthOfLongestSubstring3(char * s)
{
    int hash[127] = {0};

    int left = 0,right = 0,max =0;

    while (s[right])
    {
        if (hash[s[right]]==0)
        {
            hash[s[right++]]++;
        }
        else
        {
            hash[s[left++]]--;
        }
        max = MAX(max,(right-left));        
    }
    return max;
    
}

int main(int *argc,char *argv[])
{
    char * s ="dbbabcabc";
    int temp =0;

    temp = lengthOfLongestSubstring1(s);
    printf("algorithm1 temp =%d\n",temp);
    
    temp = lengthOfLongestSubstring2(s);
    printf("algorithm2 temp =%d\n",temp);
   
    temp = lengthOfLongestSubstring3(s);
    printf("algorithm3 temp =%d\n",temp);

}

使用hash表，记录字符出现的次数，用左右指针制造滑动窗口。如果hash为0，右指针增加，并且对应的hash表加一；如果hash不为0，左指针增加，hash减一。记录最长字符串长度。