[Leetcode] Longest Substring Without Repeating Characters

 1 public class Solution {
 2     public int lengthOfLongestSubstring(String s) {
 3         if (s == null || s.length() == 0)
 4             return 0;
 5         if (s.length() == 1)
 6             return 1;
 7         HashMap<String, Integer> hm = new HashMap<String, Integer>();
 8         int result = 0;
 9         int start = 0;
10         int end = 0;
11         int N = s.length();
12 
13         while (start != N) {
14             if (!hm.containsKey(s.charAt(start) + ""))
15                 hm.put(s.charAt(start) + "", 1);
16             for (end = start + 1; end < N; ++end) {
17                 if (hm.containsKey(s.charAt(end) + "")) {
18                     if ((end - start) > result) {
19                         result = end - start;
20                     }
21                     break;
22                 } else {
23                     hm.put(s.charAt(end) + "", 1);
24                 }
25             }
26             start++;
27         }
28         return result;
29     }
30 }

 1 package POJ;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Arrays;
 5 import java.util.HashMap;
 6 import java.util.LinkedList;
 7 import java.util.List;
 8 
 9 public class Solution {
10     public static void main(String[] args) {
11         Solution so = new Solution();
12         System.out.println(so.lengthOfLongestSubstring("wlrbbmqbhcdarzowkkyhiddqscdxrjmowfrxsjybldbefsarcbynecdyggxxpklorellnmpapqfwkhopkmco"));
13     }
14 
15     public int lengthOfLongestSubstring(String s) {
16         if (s == null || s.length() == 0)
17             return 0;
18         if (s.length() == 1)
19             return 1;
20         int[] hash = new int[256];
21         Arrays.fill(hash, -1);
22         int start = 0;
23         int end = start + 1;
24         int result = 1;
25         hash[s.charAt(0)] = 0;
26         while(end<s.length()){
27             if(hash[s.charAt(end)]>=start){
28                 start=hash[s.charAt(end)]+1;
29             }
30             result=Math.max(result, end-start+1);
31             hash[s.charAt(end)]=end;
32             end++;
33         }
34         return result;
35     }
36 }