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.

class Solution {
public:
int lengthOfLongestSubstring(string s) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
map<char, const char*> chars_map;
const char* p = s.c_str();
int max_length = 0;
int cur_length = 0;
const char* pre_char = NULL;
const char* p_begin = p;
while (*p) {
map<char, const char*>::iterator it = chars_map.find(*p);
if (it != chars_map.end()) {
if (max_length < cur_length) {
max_length = cur_length;
}
pre_char = it->second;
cur_length = p - pre_char;
while (p_begin != pre_char) {
if (*p_begin != *pre_char) {
chars_map.erase(*p_begin);
}
++p_begin;
}
it->second = p;
p_begin = ++pre_char;
++p;
} else {
chars_map.insert(make_pair(*p, p));
++cur_length;
++p;
}
}
max_length = max_length < cur_length ? cur_length : max_length;
return max_length;
}
};