leetcode solution-l03

question

Longest Substring Without Repeating Characters

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

Example 1:

Input: “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.
Example 2:

Input: “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.
Example 3:

Input: “pwwkew”
Output: 3
Explanation: 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.

track

1. when you try to find a substring without repeating characters, all characters you keeped are different, you should keep an eye on it；

code

#include <iostream>
#include <string>
#define FLAG_UNIT_LEN 128
using namespace std;

class Solution
{
public:
    int maxLength(string s)
    {
        int maxl = -1, j = 0;
        bool flag[FLAG_UNIT_LEN] = {};
        for(int i = 0; i < s.length(); i++)
        {
            while((j<s.length()) && !flag[s[j]])
            {
                maxl = maxl > (j-i+1) ? maxl : (j-i+1);
                flag[s[j]] = true;
                j++;
            }
            flag[s[i]] = false;
        }
        return maxl;
    }
};

int main()
{
    string s = "abcabcbb";
    Solution su;
    cout << su.maxLength(s) << endl;
    return 0;
}

compile

g++ -std=c++0x xxx.cpp

intresting

1. someone uses an int/char array, index is character, val response pos it appeared previous time, in that case, they need only one loop(without while(j) above), try it