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leetcode - Minimum Window Substring

2013-12-14 21:45  张汉生  阅读(192)  评论(0)    收藏  举报

 

 1 class Solution {
 2 public:
 3     //reference: http://www.cnblogs.com/remlostime/archive/2012/11/16/2774077.html
 4     string minWindow(string S, string T) {
 5         int flag[128];
 6         memset(flag, 0, sizeof(flag));
 7         int lenT = T.length();
 8         if (lenT <= 0)
 9             return "";
10         int n=0;
11         for (int i = 0; i < lenT; i++){
12             int index = (int)(T.at(i));
13             if (flag[index] == 0)
14                 n++;
15             flag[index]++;
16         }
17         int alFlag[128];
18         memset(alFlag, 0, sizeof(alFlag));
19         int numAl = 0;
20         const char * start = S.c_str();
21         const int maxNum = 1000000000;
22         int rltSize = maxNum;
23         const char* startPos = NULL;
24         const char * end = start;
25         while (*end != '\0'){
26             int index = (int)(*end);
27             alFlag[index]++;
28             if (alFlag[index] == flag[index])
29                 numAl++;
30             if (numAl == n){
31                 while (start <= end){
32                     if (rltSize > end - start + 1){
33                         rltSize = end - start + 1;
34                         startPos = start;
35                     }
36                     int ind = (int)(*start);
37                     alFlag[ind]--;
38                     if (flag[ind] !=0 && alFlag[ind] == flag[ind]-1)
39                         numAl--;
40                     if (numAl < n){
41                         start++;
42                         break;
43                     }
44                     start++;
45                 }
46             }
47             end++;
48         }
49         if (startPos == NULL)
50             return "";
51         string rlt="";
52         while (rltSize-- > 0)
53             rlt += *(startPos++);
54         return rlt;
55     }
56 };