Leetcode-3-Longest Substring Without Repeating Characters

题目描述

Given a string, find the length of the longest substring without repeating characters.

Examples:

Given “abcabcbb”, the answer is “abc”, which the length is 3.

Given “bbbbb”, the answer is “b”, with the length of 1.

Given “pwwkew”, 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.

/**
 * Longest Substring Without Repeating Characters
 * 
 * @author jiaohanhan
 *
 */
public class P3 {

    public static void main(String[] args) {
        P3 p3 = new P3();
        System.out.println(p3.lengthOfLongestSubstring("abcabcbb"));
        System.out.println(p3.lengthOfLongestSubstring("bbbb"));
        System.out.println(p3.lengthOfLongestSubstring("pwwkew"));

    }

    public int lengthOfLongestSubstring(String s) {
        int[] map = new int[256]; // ASCII码

        int j = 0;
        int i = 0;
        int ans = 0;
        for (; i < s.length(); i++) {
            while (j < s.length() && map[s.charAt(j)] == 0) {
                map[s.charAt(j)] = 1;
                ans = Math.max(ans, j - i + 1);
                j++;
            }
            map[s.charAt(i)] = 0;
        }

        return ans;
    }

}