洛谷 P1018 乘积最大（NOIp2000提高组第二题）

DP

f[i][j]表示在前i个数字中插入j个乘号时乘积的最大值

//P1018 乘积最大//2017.5.22#include <bits/stdc++.h>using namespace std;int n, k;string s;long long f[42][7];int sub(int x, int y){    int num = 0;    for (int ii = 0; ii <= y - x; ii++)        num = num * 10 + s[x + ii] - '0';    return num;}int main(){    cin >> n >> k;    cin >> s;    for (int i = 0; i < n; i++){        f[i][0] = sub(0, i);//      cout << f[i][0] << "  ";    }//  cout << endl;    for (int i = 0; i < n; i++)   //在前i个字串中         for (int j = 1; j <= min(k, i); j++)   //插入j个×             for (int p = 0; p < i; p++)   //尝试在p的后边加一个×                 f[i][j] = max(f[i][j], f[p][j - 1] * sub(p + 1, i));//  for (int i = 0; i < n; i++)//      for (int j = 0; j <= min(k, i); j++)//          cout << i << " " << j << " : " << f[i][j] << endl;    cout << f[n - 1][k];    return 0;}