2023-2-17 BM66最長公共子串

#include <vector>
class Solution {
public:
    /**
     * longest common substring
     * @param str1 string字元串 the string
     * @param str2 string字元串 the string
     * @return string字元串
     */
    string LCS(string str1, string str2) {
        // write code here
        int m = str1.size();
        int n = str2.size();
        vector<vector<int> > dp(m+1, vector<int>(n+1, 0));
        int maxLen = 0;
        int endIdx = 0;
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (str1[i-1] != str2[j-1]) {
                    dp[i][j] = 0;
                } else {
                    dp[i][j] = dp[i-1][j-1] + 1;
                }
                if (dp[i][j] > maxLen) {
                    maxLen = dp[i][j];
                    endIdx = i;
                }
            }
        }
        return str1.substr(endIdx - maxLen, maxLen);
    }
};