最长公共子字符串（动态规划）

和经典DP最长公共子串（不要求字符连续）不同，最长公共子字符串要求字符是连续的

class LongestSubstring {public:    int findLongest(string A, int n, string B, int m) {        //f[i][j] represent the longest common substring starting with A[i] and B[j]        vector<vector<int>> f(n+1, vector<int>(m+1, 0));        //maxlen is the overall max common substring length, starting anywhere        int maxlen = 0;        //dp        for(int i = n-1; i > -1; --i){            for(int j = m-1; j > -1; --j){                if(A[i] != B[j]){                    //no such common substring ended with A[i] and B[j]                    //f[i][j] remain 0 as initialized                }                else{                    //common substring starts with A[i] and B[j]                    f[i][j] = f[i+1][j+1] + 1;                    maxlen = max(maxlen, f[i][j]);                }            }        }        return maxlen;    }};