leetcode-Three

Longest Substring Without Repeating Characters

java

description:

Input: "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

class Solution {
    public int lengthOfLongestSubstring(String s) {
        Set<Character> newHashSet = new HashSet<>();
        int length = 0;
        int maxLength = 0;
        int index = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (!newHashSet.contains(c)) {
                newHashSet.add(c);
                length++;
            } else {
                while (s.charAt(index) != c) {
                    newHashSet.remove(s.charAt(index));
                    index++;
                }
                index++;
                length = i + 1 - index;
            }
          maxLength = Math.max(length,maxLength);
        }
        return maxLength;
    }
}

java解题思路

1. 首先初始化一个Hashset(newHashSet),定义三个int变量length，maxLength,index,初始值都为0
2. for循环Sting变量s
3. 每次循环将s的当前字符赋值给char变量c
4. if用来判断当前字符在newHashSet是否存在
5. 如果不存在则添加字符到newHashSet中，长度加1
6. 如果存在则进行while循环，删除重复的字符第一次出现的位置
7. index长度加1，用来下次字符相同时，直接从index位置开始判断
8. 计算当前长度
9. 使用max函数将最大值赋值给maxLength
10. 返回maxLength