题解 | #最长公共子串#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * longest common substring
     * @param str1 string字符串 the string
     * @param str2 string字符串 the string
     * @return string字符串
     */
    public String LCS (String str1, String str2) {
        final int N = str1.length();
        final int M = str2.length();

        int[][] maxLen = new int[N + 1][M + 1];

        int len = 0;
        int end = 0;
        for (int i = 0; i != N; i++) {
            for (int j = 0; j != M; j++) {
                char c1 = str1.charAt(i);
                char c2 = str2.charAt(j);
                if (c1 == c2) {
                    maxLen[i + 1][j + 1] = maxLen[i][j] + 1;
                }

                if (maxLen[i + 1][j + 1] > len) {
                    len = maxLen[i + 1][j + 1];
                    end = i;
                }
            }
        }
        return str1.substring(end - len + 1, end + 1);
    }
}