【模式匹配】— KMP变形

求STR中所有的匹配sub位置，和基本KMP略有不同

package base;

//O(m+n) 时间复杂度 KMP主要是求Next数组 
public class KMP {

    public static int[] next(String sub) {
        int[] a = new int[sub.length()];
       char[] c = sub.toCharArray();
        int length=sub.length();
        int i,j;
        a[0] = -1;
        i = 0;
       for(j=1;j<length;j++) {
           i = a[j - 1];
           while(i>=0&&c[j]!=c[i+1]) {
               i = a[i];    
           }
          if(c[j]==c[i+1]) {
              a[j] = i+1;
          }
          else {
              a[j] = -1;
          }
       }
       return a;
   }
    
    public static void pattern(String str,String sub,int[] next) {          
        char[] ch1 = str.toCharArray();           
        char[] ch2 = sub.toCharArray();           
        int i = 0,j = 0;  // i控制ch1,j控制ch2;
         for(;i<ch1.length;) {
             if(ch1[i]==ch2[j]){// 匹配就自动递增，往后匹配。
                 if(j==ch2.length-1){
                     System.out.println(i-ch2.length+1);
                     break;
                 }
                 j++;
                 i++;
             }
             else if(j==0){
                     i++;
             }
            else{ 
                j=next[j-1]+1;
            }
        }
    }
                                                                                                                                                                                        
    
    public static void main(String[] args) {
        
        String sub = "ababca";        
        String str = "bababcababababcabab";        
        int[] next = next(sub);
        pattern(str,sub,next);
    }
}