dynamic programming:最长公共子串

import java.util.*;


public class Solution {
    /**
     * 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[][] lcs = new int[str1.length() + 1][str2.length() + 1];
        int max = 0;
        int index = 0;
        for (int i = 1; i <= str1.length(); i++) {
            for (int j = 1; j <= str2.length(); j++) {
                if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
                    lcs[i][j] = lcs[i - 1][j - 1] + 1;
                    if (lcs[i][j] > max) {
                        max = lcs[i][j];
                        index = i;
                    }
                }
            }
        }
        return str1.substring(index - max, index);
    }
}