lintcode:Longest Substring Without Repeating Characters

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

Example

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

.

Challenge

O(n) time

class Solution {
public:
/**
* @param s: a string
* @return: an integer
*/
int lengthOfLongestSubstring(string s) {
// write your code here
vector<int> dp(s.size()+1);
map<int, int> posMap;

dp[0] = 0;
int retMax = 0;

for (int i=0; i<s.size(); i++)
{
if (posMap.count(s.at(i)) == 0)
{
dp[i+1] = dp[i]+1;
}
else
{
dp[i+1] = min(i-posMap[s.at(i)], dp[i]+1);
}

posMap[s.at(i)] = i;

retMax = max(retMax, dp[i+1]);
}

return retMax;
}
};