题目链接:https://leetcode.com/problems/longest-substring-without-repeating-characters/description/
题目大意:找出string中最长不重复子串
思路:
一开始我是想着暴力解决,用start and end两个指针遍历,这样会有n2的复杂度,超时,因此查看了其他博客,比如这个http://blog.csdn.net/feliciafay/article/details/16895637才发现有O(n)的解法,主要思路是依旧是用两个指针指定子串开始和末尾,
用map<char, int>来存储扫过的char以及其索引,一旦遇到重复,停止扫描,比较长度,然后从子串里重复的元素的索引+1处开
始新一轮遍历。
代码:
class Solution {
public:
int lengthOfLongestSubstring(string s) {
int start = 0;
int end = 0;
int maxLen = 0;
int slen = s.length();
map<char, int> localMap;
while(start < slen && end < slen) {
end = start;
localMap.clear();
while(end < slen && localMap.find(s[end]) == localMap.end()) {
localMap[s[end]] = end;
end++;
}
int length = end - start;
maxLen = length > maxLen ? length : maxLen;
start = localMap[s[end]] + 1;
}
return maxLen;
}
};