Longest Substring Without Repeating Characters(C語言實現)，longestrepeating

Longest Substring Without Repeating Characters(C語言實現)，longestrepeating

Given a string, find the length of the longest substring without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

 題目地址：https://leetcode.com/problems/longest-substring-without-repeating-characters/

題目意思：給出一個字符串，輸出最長的子串的長度，子串不能有重復的字符。（子串是連續的。）

解題思路：   依次讀取字符串的每一個字符，如果第一次出現則當前子串長度+1，否則：首先判斷當前長度是否大於最大長度，是則替換最大長度。然後

　　　　　　查找重復的字符是在原字符串哪裡出現的。

代碼如下：

 1 int lengthOfLongestSubstring(char* s) {
 2     int maxlen = 0,currlen = 0;
 3     int table[128], i, j, start = 0;
 4     memset(table, 0, sizeof(table));
 5     for (i = 0; s[i] != '\0'; ++i){
 6         if( (++table[s[i]]) == 2 ){
 7             if (currlen > maxlen){
 8                 maxlen = currlen;
 9             }
10             for(j = start; j < i; ++j){ //start記錄重復的字符後一個位置
11                 if (s[j] == s[i]){
12                     table[s[j]] = 1;
13                     start = j+1;
14                     break;
15                 }else{
16                     --currlen;
17                     table[s[j]] = 0;
18                 }
19             }
20         }else{
21             ++currlen;
22         }
23     }
24     if (currlen > maxlen){
25         maxlen = currlen;
26     }
27     return maxlen;
28 }