leetcode-3. Longest Substring Without Repeating Characters

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.

Subscribe to see which companies asked this question

class Solution {
public:
int lengthOfLongestSubstring(string s) {
//遍历，hash表存，key为字符，value为对应下标，
//两个指针一左一右，右的往后遍历并让字符入hash，当重复时左指针移到对应下标的下一个
if(s.size() == 0)
{
return 0;
}
int left = 0;
int right = 0;
int result = 0;
map<char,int> myMap;
for(int i=0;i<s.size();i++)
{
right = i;
//找到了
if(myMap.find(s[i]) != myMap.end())
{
//如果在left前面的话还要更新index
if(myMap[s[i]] < left)
{
myMap[s[i]] = i;
continue;
}
//这时要先保存目前为止的最长子串，不包括最后一个字符，不加1
if(result < right - left)
{
result = right - left;
}
left =  myMap[s[i]] + 1;
//更新相同字符index
myMap[s[i]] = i;
}
else
{
myMap.insert(make_pair(s[i],i));
}
}
return max(result,right - left+1);
}
};