java匹配字符串并打标 java实现字符串匹配

代码：

package com.wangyq.datastructrue.arithmetic;

import java.util.Arrays;

public class KMP {
    public static void main(String[] args) {
        String str = "abcabaabaabcacb";
        String matchStr = "abaabcac";
        int index = kmp(str, matchStr);
        System.out.println("字符串所在位置：" + index);
    }

    private static int kmp(String str, String matchStr) {
        char[] strChars = str.toCharArray();
        char[] matchChars = matchStr.toCharArray();

        //首先建立对应数组
        int[] next = getNext(matchStr);
        System.out.println("部分匹配数组:" + Arrays.toString(next));
        int k = 0;
        //循环进行匹配
        for (int i = 0; i < strChars.length; i++) {
            if (strChars[i] == matchChars[k]) {
                k++;
                //判断是否匹配成功
                if (k == matchChars.length) {
                    return i - k + 1;
                }
            } else if (k != 0) {
                //匹配失败，重置i和k；
                i = i - next[k - 1];
                i--;
                k = 0;
            }
        }
        return -1;
    }

    private static int[] getNext(String matchStr) {
        char[] matchChars = matchStr.toCharArray();
        int[] next = new int[matchChars.length];
        int k;
        //for循环控制后缀
        for (int i = 1; i < matchChars.length; i++) {
            //获取前一个元素的值
            k = next[i - 1];
            if (matchChars[i] == matchChars[k]) {
                next[i] = k + 1;
            } else {
                //重置k
                if (matchChars[i] == matchChars[0]) {
                    next[i] = 1;
                } else {
                    next[i] = 0;
                }
            }
        }
        return next;
    }
}

运行结果：
部分匹配数组:[0, 0, 1, 1, 2, 0, 1, 0]
字符串所在位置：6