【HackerRank】Common Child (LCS)最长公共子序列

Given two strings a and b of equal length, what’s the longest string (S) that can be constructed such that S is a child to both a and b.

String x is said to be a child of string y if x can be formed by deleting 0 or more characters from y

Input format

Two strings a and b with a newline separating them

Constraints

All characters are upper-cased and lie between ascii values 65-90The maximum length of the strings is 5000

Output format

Length of the string S

Sample Input #0

HARRY
SALLY

Sample Output #0

2

The longest possible subset of characters that is possible by deleting zero or more characters from HARRY and SALLY is AY, whose length is 2.

Sample Input #1

AA
BB

Sample Output #1

0

AA and BB has no characters in common and hence the output 0

Sample Input #2

SHINCHAN
NOHARAAA

Sample Output #2

3

The largest set of characters, in order, between SHINCHAN and NOHARAAA is NHA.

Sample Input #3

ABCDEF
FBDAMN

Sample Output #3

2

import java.util.Scanner;
import java.lang.String;
import java.lang.Math;

/*
class TreeNode
{
	int val;
	TreeNode left;
	TreeNode right;
	TreeNode(int x) { val = x; left = null; right = null;}
}
class ListNode
{
	int val;
	ListNode next;
	ListNode(int x){val = x; next = null;}
}
*/
public class Solution {
	

	public static void main(String[] args) 
	{
		//int T;
		Scanner jin = new Scanner(System.in);
		//T = jin.nextInt();
		String str1 = jin.next();
		String str2 = jin.next();
		int len = str1.length();
		int[][] array = new int[len+1][len+1];
		for(int i = 0; i < len+1; i++)
			array[0][i] = array[i][0] = 0;
		for(int i = 0; i < len; i++)
		{
			for(int j = 0; j < len; j++)
			{
				if (str1.charAt(i) == str2.charAt(j)) {
					array[i+1][j+1] = array[i][j] + 1;
				}
				else {
					array[i+1][j+1] = Math.max(array[i][j+1], array[i+1][j]);
				}
			}
		}
		System.out.println(array[len][len]);
		array = null;
	}
	
}