poj2184 Cow Exhibition

思路：

dp+滚动数组。

类似01背包。

实现：

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 using namespace std;

 const int INF = 0x3f3f3f3f;
 const int t = ;
 int a[], b[], dp[][], n, p, q;
 int solve(int n)
 {
     for (int i = ; i < ; i++)
     {
         for (int j = -t; j <= t; j++)
         {
             dp[i][j + t] = -INF;
         }
     }
     for (int i = ; i < ; i++)
         dp[i][a[i] + t] = b[i];
     for (int i = ; i < n; i++)
     {
         for (int j = -t; j <= t; j++)
         {
             dp[i & ][j + t] = max(dp[(i - ) & ][j + t], dp[i & ][j + t]);
             if (j + t - a[i] <  || j + t - a[i] > )
                 continue;
             dp[i & ][j + t] = max(dp[i & ][j + t], dp[(i - ) & ][j + t - a[i]] + b[i]);
         }
     }
     int ans = -INF;
     for (int j = ; j <= t; j++)
     {
         ans = max(ans, dp[(n - ) & ][j + t] >=  ? j + dp[(n - ) & ][j + t] : -INF);
     }
     return ans;
 }

 int main()
 {
     cin >> n;
     int cnt = ;
     for (int i = ; i < n; i++)
     {
         cin >> p >> q;
         if (p <  && q < )
             continue;
         a[cnt] = p;
         b[cnt++] = q;
     }
     int ans = solve(cnt);
     if (ans <= -INF)
         cout << "" << endl;
     else
         cout << ans << endl;
     return ;
 }