TC_SRM471 Div2 500

 

动态规划Code：

#include <algorithm>#include <bitset>#include <cassert>#include <cctype>#include <climits>#include <cmath>#include <complex>#include <cstdio>#include <cstdlib>#include <cstring>#include <ctime>#include <deque>#include <fstream>#include <functional>#include <iomanip>#include <iostream>#include <limits>#include <list>#include <map>#include <numeric>#include <queue>#include <set>#include <sstream>#include <stack>#include <string>#include <utility>#include <vector>using namespace std;int MOD = 1000000007;class EllysPlaylists{public:int countPlaylists(vector <string> songs, int K);bool isSmooth(string a, string b);protected:private:};bool EllysPlaylists::isSmooth(string a, string b){for (int i=0; i<3; i++){if(a[i] != b[b.length()-3 + i])return false;}return true;}int EllysPlaylists::countPlaylists(vector<string> songs, int K){int ans = 0;int n = songs.size();vector<vector<int> > dp(n, vector<int>(K+1));for (int i=0; i<n; i++)dp[i][1] = 1;for (int k=2; k<=K; k++){for (int i=0; i<n; i++){for (int j=0; j<n; j++){if(isSmooth(songs[i],songs[j])){dp[i][k]=(dp[i][k]+dp[j][k-1])%MOD;}}}}for (int i=0; i<n; i++){ans = (ans + dp[i][K])%MOD;}return ans;}