LeetCode longest substring without repeating characters 题解 Hash表
2024-08-30 00:20:03
题目
Given a string, find the length of the longest substring without repeating characters.
Example 1:
Input: “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.
Example 2:
Input: “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.
Example 3:
Input: “pwwkew”
Output: 3
Explanation: The answer is “wke”, with the length of 3.
Note that the answer must be a substring, “pwke” is a subsequence and not a substring.
思路——Hash大法好
双指针移动。
Hash表查询字符是否出现。
时间复杂度O(L)O(L)O(L),空间复杂度O(L)O(L)O(L)
结果
Runtime: 27 ms, faster than 70.11% of Java online submissions for Longest Substring Without Repeating Characters.
Memory Usage: 37.5 MB, less than 100.00% of Java online submissions for Longest Substring Without Repeating Characters.
源码
class Solution {
public int lengthOfLongestSubstring(String s) {
Set<Character> set = new HashSet<Character>();
int ans = 0;
int l, r = 0;
Character c;
int len = s.length();
for (l = 0; l < len; ++l) {
while (r < len) {
c = s.charAt(r);
if (set.contains(c)) {
ans = Math.max(ans,r-l);
break;
} else {
set.add(c);
++r;
}
}
if (r == len) {
ans = Math.max(ans, r - l);
break;
}
set.remove(s.charAt(l));
}
return ans;
}
}
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