LeetCode-in-All
3. Longest Substring Without Repeating Characters
Medium
Given a string s, find the length of the longest substring without duplicate 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 * 104sconsists of English letters, digits, symbols and spaces.
Solution
func lengthOfLongestSubstring(s string) int {
lastIndices := make([]int, 256)
for i := 0; i < 256; i++ {
lastIndices[i] = -1
}
maxLen := 0
curLen := 0
start := 0
for i := 0; i < len(s); i++ {
cur := s[i]
if lastIndices[cur] < start {
lastIndices[cur] = i
curLen++
} else {
lastIndex := lastIndices[cur]
start = lastIndex + 1
curLen = i - start + 1
lastIndices[cur] = i
}
if curLen > maxLen {
maxLen = curLen
}
}
return maxLen
}