【LeetCode】 3. Longest Substring Without Repeating Characters 无重复字符的最长子串 （Medium）（JAVA）
题目地址: https://leetcode.com/problems/longest-substring-without-repeating-characters/
题目描述：
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.
题目大意
给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。
解题方法
用一个变量记录开始的位置，用一个数组来记录是否有过当前字母；
遇到有过当前字母，从开始的位置开始不断往后遍历，直到找到相同字母为止，同时减去遍历过的字母。
Accepted
class Solution {
public int lengthOfLongestSubstring(String s) {
int max = 0;
int[] count = new int[128];
int start = 0;
for (int i = 0; i < s.length(); i++) {
if (count[s.charAt(i)] == 0) {
count[s.charAt(i)]++;
} else {
while (s.charAt(i) != s.charAt(start)) {
count[s.charAt(start)]--;
start++;
}
start++;
}
if ((i - start + 1) > max) max = i - start + 1;
}
return max;
}
}
执行用时 : 4 ms, 在所有 Java 提交中击败了91.09%的用户
内存消耗 : 38.9 MB, 在所有 Java 提交中击败了12.34%的用户
