参考回答：
int substr(string & str1, string &str2){int len1 = str1.length();int len2 = str2.length();vector<vector<int>>dp(len1,vector<int>(len2,0));for (int i = 0; i < len1; i++){dp[i][0] = str1[i]==str1[0]?1:0;}for (int j = 0; j <= len2; j++){dp[0][j] = str1[0]==str2[j]?1:0;}for (int i = 1; i < len1; i++){for (int j = 1; j < len2; j++){if (str1[i] == str2[j]){dp[i][j] = dp[i - 1][j - 1]+1;}}}int longest = 0;int longest_index = 0;for (int i = 0; i < len1; i++){for (int j = 0; j < len2; j++){if (longest < dp[i][j]){longest = dp[i][j];longest_index = i;}}}//字符串为从第i个开始往前数longest个 for (int i = longest_index-longest+1; i <=longest_index; i++) { cout << str1[i] << endl; } return longest;}
