Leetcode第三题--无重复字符的最长子串（c实现）

给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。

示例 1:

输入: "abcabcbb"
输出: 3 
解释: 因为无重复字符的最长子串是 "abc"，所以其长度为 

int lengthOfLongestSubstring(char* str) {

    int n = strlen(str);

    if(!n) return 0;

    int L_len = 1;          // lenght of longest substring
    int C_len = 1;          // lenght of current substring

    int P_ind, i;           //  P_ind for previous index
    int visited[256];       //  visited will keep track of visiting char for the last instance.
                            //  since there are 256 ASCII char, its size is limited to that value.
    memset(visited, -1, sizeof(int) * 256);
    visited[str[0]] = 0;        //  the index of that char will tell us that when it was visited.
    for (i = 1; i < n; i++)
    {
        P_ind =  visited[str[i]];
        if (P_ind == -1 || i - C_len > P_ind)
            C_len++;        //  if the current char was not visited earlier, or it is not the part of current substring
        else
        {                           //  otherwise, we need to change the current/longest substring length
            if (C_len > L_len) L_len = C_len;
            C_len = i - P_ind;
        }
        visited[str[i]] = i;
    }
    if (C_len > L_len) L_len = C_len;
    return L_len;
}