leetcode刷题（java）——nums【3】

problem：

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.

solution

Java String charAt()方法此方法返回位于字符串的指定索引处的字符。该字符串的索引从零开始。

/*
 * @lc app=leetcode id=3 lang=java
 *
 * [3] Longest Substring Without Repeating Characters
 */
class Solution {
    public int lengthOfLongestSubstring(String s) {

        int result = 0;
        int[] cache = new int[256];
        for (int i = 0, j = 0; i < s.length(); i++) {
            j = (cache[s.charAt(i)] > 0) ? Math.max(j, cache[s.charAt(i)]) : j;
            cache[s.charAt(i)] = i + 1;
            result = Math.max(result, i - j + 1);
        }
        return result;

    }
}