题解 | #最长公共子串#

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * longest common substring
     * @param str1 string字符串 the string
     * @param str2 string字符串 the string
     * @return string字符串
     */
    string LCS(string str1, string str2) {
        // write code here
        int n1 = str1.length();
        int n2 = str2.length();
        int max = 0;
        int pos = 0;
        vector<vector<int>>dp(n1+1,vector<int>(n2+1));
        for(int i = 1;i<=n1;i++)
        {
            for(int j = 1;j<=n2;j++)
            {
                if(str1[i-1]==str2[j-1])
                {
                    dp[i][j] = dp[i-1][j-1]+1;
                }
                else{
                    dp[i][j]=0;
                }
                if(dp[i][j]>max)
                {
                    max = dp[i][j];
                    pos = i-1;
                }
            }
        }
        return str1.substr(pos-max+1,max);

    }
};