Leetcode 76: Minimum Window Substring

 1 public class Solution {
 2     public string MinWindow(string s, string t) {
 3         if (s == "" || t == "") return "";
 4         
 5         var dict = new Dictionary<char, int>();
 6         
 7         for (int i = 0; i < t.Length; i++)
 8         {
 9             if (dict.ContainsKey(t[i]))
10             {
11                 dict[t[i]]++;
12             }
13             else
14             {
15                 dict[t[i]] = 1;
16             }
17         }
18         
19         int start = 0, j = 0, count = t.Length;
20         var result = "";
21         
22         while (j < s.Length)
23         {
24             if (dict.ContainsKey(s[j]))
25             {
26                 if (dict[s[j]] > 0)
27                 {
28                     count--;
29                 }
30                 
31                 dict[s[j]]--;
32             }
33             
34             while (count == 0 && start <= j)
35             {
36                 if (result == "" || result.Length > j - start + 1)
37                 {
38                     result = s.Substring(start, j - start + 1);
39                 }
40                 
41                 if (dict.ContainsKey(s[start]))
42                 {
43                     dict[s[start]]++;
44                     
45                     if (dict[s[start]] > 0)
46                     {
47                         count++;
48                     }
49                 }
50                 
51                 start++;
52             }
53             
54             j++;
55         }
56         
57         return result;
58     }
59 }