vijos 1037 ***

链接：点我

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <iostream>
 using namespace std;
 const int v =  + ;
 const int MaxN =  + ;
 int N, sum, num[MaxN], dp[][v];
 int main() {
     int i, j, k;
     cin >> N;
     for(i = ; i < N; ++i) {
         cin >> num[i];
         sum += num[i];
     }
     memset(dp, -, sizeof(dp));
     dp[][] = ;
     int a;
     for(i = ; i < N; ++i) {
         a = i % ;
         memset(dp[a], -, sizeof(dp[a]));
         for(j = ; j <= sum; ++j) {
             //1.不放第i块水晶;
             if(dp[a ^ ][j] > -)
                 dp[a][j] = dp[a ^ ][j];
             //2.放进去后，高塔变矮塔（第i块放在矮塔上了）;
             if(num[i] > j &&  dp[a ^ ][num[i] - j] > -)
                 dp[a][j] = max(dp[a][j], dp[a ^ ][num[i] - j] + j);
             //3.放进去后，高塔仍高（第i块放在矮塔上）;
             if(j + num[i] <= sum && dp[a ^ ][j + num[i]] > -)
                 dp[a][j] = max(dp[a][j], dp[a ^ ][j + num[i]]);
             //4.放进去后，高塔更高（第i块放在高塔上）.
             if(j >= num[i] && dp[a ^ ][j - num[i]] > -)
                 dp[a][j] = max(dp[a][j], dp[a ^ ][j - num[i]] + num[i]);
         }
     }
     if(dp[a][] > )
         cout << dp[a][] << endl;
     else
         cout << "Impossible" << endl;
 }