题解 | #查找两个字符串a,b中的最长公共子串#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String a = in.nextLine();
            String b = in.nextLine();
            System.out.println(getMaxStr(a, b));
        }
    }
    private static String getMaxStr(String a, String b) {
        //刚开始一直没有注意 输出短字符串先出现的，栽了了好几次
        if (a.length() > b.length()) {
            String temp = a;
            a = b;
            b = temp;
        }
        int[][] dp = new int[a.length() + 1][b.length() + 1];
        if (a.length() == 0) {
            for (int i = 0; i < a.length() + 1; i++) {
                dp[0][i] = 0;
            }
        }
        if (b.length() == 0) {
            for (int i = 0; i < b.length() + 1; i++) {
                dp[i][0] = 0;
            }
        }
        int idx = -1;
        int res = 0;

        for (int i = 1; i < a.length() + 1; i++) {
            for (int j = 1; j < b.length() + 1; j++) {
                if (a.charAt(i - 1) == b.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                } else {
                    dp[i][j] = 0;
                }
                if (dp[i][j] > res) {
                    res = dp[i][j];
                    idx = i - res;
                }
            }
        }
        return a.substring(idx, idx + res);
    }
}