KMP（Java）

理论参考-》

package com.answer.kmp;

public class Test1 {
    public int ViolentMatch(String str1,String str2){
        char[] c1=str1.toCharArray();
        char[] c2=str2.toCharArray();
        int l1=c1.length;
        int l2=c2.length;
        int[] next=new int[l2];
        GetNext(str2,next);
        int i=0,j=0;
        while(i<l1&&j<l2){
            if(j==-1||c1[i]==c2[j]){
                i++;
                j++;
            }else {
                j=next[j];
            }
        }
        if(j==l2){
            return i-j;
        }else {
            return -1;
        }
    }
    public void GetNext(String str2,int[] next){
        char[] c2=str2.toCharArray();
        int l2=c2.length;
        next[0]=-1;
        int k=-1;
        int j=0;
        while (j<l2-1){
            if(k==-1||c2[k]==c2[j]){
                ++k;
                ++j;
                if(c2[j]!=c2[k]){
                    next[j]=k;
                }else {
                    next[j]=next[k];
                }
                //next[j]=k;
            }else {
                k=next[k];
            }
        }
    }

    public static void main(String[] args) {
        int pos=new Test1().ViolentMatch("abacababc","abab");
        System.out.println(pos);
    }
}