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) {
        // write code here

        int maxLength = 0;
        int maxLastIndex = 0;
        int[][] dp = new int[str1.length() + 1][str2.length() + 1];

        for (int i = 0; i < str1.length(); i++) {

            for (int j = 0; j < str2.length(); j++) {
                if (str1.charAt(i) == str2.charAt(j)) {
                    dp[i + 1][j + 1] = dp[i][j] + 1;

                    if (dp[i + 1][j + 1] > maxLength) {
                        maxLength = dp[i + 1][j + 1];
                        maxLastIndex = i;
                    }
                } else {
                    dp[i + 1][j + 1] = 0;
                }
            }
        }

        return str1.substring(maxLastIndex - maxLength + 1, maxLastIndex + 1);
    }
}