3. Longest Substring Without Repeating Characters

Medium
​
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 * 104
  • s consists of English letters, digits, symbols and spaces.

解題

func lengthOfLongestSubstring(s string) int {
ans := 0
start := 0
m := make(map[byte]int)
​
for index := 0; index < len(s); index++ {
if val, ok := m[s[index]]; ok {
if start < val+1 {
start = val + 1
}
}
if index-start+1 > ans {
ans = index - start + 1
}
​
m[s[index]] = index
}
​
return ans
}