查找两个字符串a,b中的最长公共子串

题目：牛客网

解题思路：

使用动态规划，

2个字符串中短字符串的长度作为数组(record)的行数

长字符串的长度作为数组(record)的列数

判断两个字符是否相等，若不相等，record[i][j]=0；若相等，需要注意row==0或col==0的情况，此时,record[i][j]==1；

i!=0且j!=0的时候，record[i][j]=record[i-1][j-1]+1

	a	b	c	d	e	f
a	1	0	0	0	0	0
a	1	0	0	0	0	0
b	0	2	0	0	0	0
c	0	0	3	0	0	0

 

 

import java.util.Scanner;

public class Main {
	public static void findLongestSequence(String str_short, String str_long){
		int row = str_short.length();
		int col = str_long.length();
		int[][] record = new int[row][col];
		int max_len = 0;
		int row_pos = 0;
		for(int i = 0; i < str_short.length(); i++ ){
			for(int j = 0; j < str_long.length(); j++){
				if(str_short.charAt(i) != str_long.charAt(j)){
					record[i][j]=0;
				}
				else{
					if(i == 0 || j == 0){
						record[i][j] = 1;
						if(max_len < record[i][j]){
							max_len = record[i][j];
							row_pos = i;
						}
					}
					else{
						record[i][j] = record[i-1][j-1]+1;
						if(max_len < record[i][j]){
							max_len = record[i][j];
							row_pos = i;
						}
					}
				}
			}
		}
		System.out.println(str_short.substring(row_pos+1-max_len,row_pos+1));
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner(System.in);
		while(in.hasNext()){
			String str1 = in.next();
			String str2 = in.next();
			int str1_len = str1.length();
			int str2_len = str2.length();
			if(str1_len > str2_len)
				findLongestSequence(str2,str1);
			else
				findLongestSequence(str1,str2);
			
		}
	}

}