题解 | #最长公共子串#

class Solution {
public:
    /**
     * 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 l1 = str1.size(),l2 = str2.size();
        int rec[l2];
        memset(rec,0,sizeof(rec));
        vector<int> ret{0,0};
        auto up = [=,&ret](int a,int b){
            ret[0] = a;
            ret[1] = b;
        };
        for(int i=0;i<l1;i++){
            for(int j=l2;j>=0;j--){
                if(str1[i] == str2[j]){
                    rec[j] = rec[j-1] + 1;
                }else{
                    rec[j] = 0;
                }
                //rec[i][j] = max(rec[i][j],rec[i-1][j]);
                //rec[i][j] = max(rec[i][j],rec[i][j-1]);
                if(rec[j] > ret[1])
                    up(i,rec[j]);
            }
        }
        
        return str1.substr(ret[0]-ret[1]+1, ret[1]);
    }
};