Today I have done leetcode's June LeetCoding Challenge with cpp.

June LeetCoding Challenge 10

Description

Longest Substring Without Repeating Characters

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

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

• 0 <= s.length <= 5 * 10^4
• s consists of English letters, digits, symbols and spaces.

Solution

class Solution {
public:
  int lengthOfLongestSubstring(string s) {
    bool has[128] = {false};
    int head = 0, tail = 0;
    int answer = 0;
    int len = s.length();
    while(head < len) {
      if(!has[s[head]]) {
        has[s[head]] = true;
        ++head;
        answer = max(head-tail, answer);
      } else {
        while(has[s[head]]) {
          has[s[tail]] = false;
          ++tail;
        }
      }
    }
    return answer;
  }
};

// Accepted
// 987/987 cases passed (4 ms)
// Your runtime beats 96.63 % of cpp submissions
// Your memory usage beats 89.6 % of cpp submissions (7 MB)