————2020.1.17————

 1 public static int[] getNext(String str) {
 2     int[] next = new int[str.length()];
 3     next[0] = -1;
 4     int i = 1, curMatch = 0;
 5     while (i<str.length()-1) {
 6         if (str.charAt(i) == str.charAt(curMatch)) {
 7             next[i+1] = next[i] + 1;
 8             curMatch++;
 9         } else {
10             next[i+1] = 0;
11             curMatch = 0;
12         }
13         i++;
14     }
15     return next;
16 }

 1 public static int KMP(String s, String t) {
 2     int[] next = getNext(t);
 3     int i = 0, j = 0;
 4     while (i < s.length() && j<t.length()) {
 5         if (j == -1 || s.charAt(i) == t.charAt(j))  
 6         {  
 7             i++;  
 8             j++;  
 9         }  
10         else  
11         {      
12             j = next[j];  
13         }  
14     }
15     if (j == t.length()) 
16         return i - j ;
17     else 
18         return -1;
19 }