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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
object Solution {
def lengthOfLongestSubstring(s: String): Int = {
val lastIndices = Array.fill(256)(-1)
var maxLen = 0
var curLen = 0
var start = 0
for (i <- 0 until s.length) {
val cur = s.charAt(i)
if (lastIndices(cur) < start) {
lastIndices(cur) = i
curLen += 1
} else {
val lastIndex = lastIndices(cur)
start = lastIndex + 1
curLen = i - start + 1
lastIndices(cur) = i
}
if (curLen > maxLen) {
maxLen = curLen
}
}
maxLen
}
}