HJ65查找两个字符串a,b中的最长公共子串（medium,dp,进入题目后题目序号是HJ21）

题目描述

思路

比如字符串s1,s2,首先，保证s1是较短的字符串。动态规划i,j位置依赖i-1,j-1位置。依赖关系不难。

Java答案

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 caseString a = in.next();String b = in.next();System.out.println(commonstr(a, b));}}public static String commonstr(String small, String big) {if (small.length() > big.length()) { //保证small是短的String tmp = small;small = big;big = tmp;}int n = small.length();int m = big.length();int[][] dp = new int[n + 1][m + 1];int maxLen = 0;int endIdx = 0;for (int i = 1; i <= n ; i++) {for (int j = 1; j <= m ; j++) {if (small.charAt(i - 1) == big.charAt(j - 1)) {dp[i][j] = dp[i - 1][j - 1] + 1;if (dp[i][j] > maxLen) {maxLen = dp[i][j];endIdx = i;}} else {dp[i][j] = 0;}}}return small.substring(endIdx - maxLen, endIdx);}
}