LeetCode-in-All
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.
Example 4:
Input: s = “”
Output: 0
Constraints:
0 <= s.length <= 5 * 104sconsists of English letters, digits, symbols and spaces.
Solution
class Solution {
int lengthOfLongestSubstring(String s) {
List<int> lastIndices = List.filled(256, -1);
int maxLen = 0;
int curLen = 0;
int start = 0;
for (int i = 0; i < s.length; i++) {
// Getting ASCII value of the character
int cur = s.codeUnitAt(i);
if (lastIndices[cur] < start) {
lastIndices[cur] = i;
curLen++;
} else {
int lastIndex = lastIndices[cur];
start = lastIndex + 1;
curLen = i - start + 1;
lastIndices[cur] = i;
}
if (curLen > maxLen) {
maxLen = curLen;
}
}
return maxLen;
}
}