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hdu 4939 Stupid Tower Defense
Stupid Tower Defense
Time Limit: 12000/6000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 1589 Accepted Submission(s): 452
The map is a line, which has n unit length. We can build only one tower on each unit length. The enemy takes t seconds on each unit length. And there are 3 kinds of tower in this game: The red tower, the green tower and the blue tower.
The red tower damage on the enemy x points per second when he passes through the tower.
The green tower damage on the enemy y points per second after he passes through the tower.
The blue tower let the enemy go slower than before (that is, the enemy takes more z second to pass an unit length, also, after he passes through the tower.)
Of course, if you are already pass through m green towers, you should have got m*y damage per second. The same, if you are already pass through k blue towers, the enemy should have took t + k*z seconds every unit length.
FSF now wants to know the maximum damage the enemy can get.
The first line contains an integer T (T<=100), indicates the number of cases.
Each test only contain 5 integers n, x, y, z, t (2<=n<=1500,0<=x, y, z<=60000,1<=t<=3)
题目给出一条长度为n的直线 , 你可以在长度为1的单元上面建造塔。
有三种类型的塔
颜色 效果
red 经过这个塔的时候,收到 x (d / s) 的伤害
green 经过这个塔之后 , 受到 y (d / s) 的持续伤害
bule 经过这个塔之后 , 经过1个塔的时间增加 z 秒
题目要求 , 求出在直线上放置n个塔 , 使得经过直线后受到的伤害最大。
然后可想而知, 红色无论放多少个。 最后放肯定是没错的 , 因为能够得到蓝色的叠加时间 , 伤害效果尽量大。
剩下就是蓝色跟绿色 , 应该怎么放。
这时候就要用到DP了 。
dp[i][j] 。。。表示前 i + j (<=n ) 个长度 i 个放green , j 个放blue 所得到的最大伤害 。
转移就是这样取就好了
dp[i][j] = max( dp[i-1][j] + ( j * z + t ) * y * ( i - 1 ) , dp[i][j-1] + ( ( j - 1 ) * z + t ) * y * i );
注意一下边界 。
然后最后要补上 red 塔的伤害就得出答案了~
#include <cstdio>#include <iostream>#include <cstring>using namespace std;typedef long long ll;const int N = 1550 ;ll dp[N][N]; // i = green , j = blue ...int main(){ ll _ , n , x , y , z , t , cas = 1; #ifdef LOCAL freopen("in","r",stdin); #endif cin >> _ ; while( _ -- ){ cin >> n >> x >> y >> z >> t ; cout << "Case #"<< cas++ <<": "; memset(dp,0,sizeof dp); for( int i = 1 ; i <= n ; ++i ){ for( int j = 0 ; j <= i ; ++j ){ int k = i - j ; ll temp = 0 ; if( j > 0 ) temp = max( temp , dp[j-1][k] + ( k * z + t ) * y * ( j - 1 ) ); if( k > 0 ) temp = max( temp , dp[j][k-1] + ( ( k - 1 ) * z + t ) * y * j ) ; dp[j][k] = temp ; } } ll ans = 0 ; for( int i = 0 ; i <= n ; ++i ){ for( int j = 0 ; j + i <= n ; ++j ){ ans = max ( ans , dp[i][j] + ( n - i - j ) * ( x * ( t + z * j ) + i * y * ( t + z * j ) ) ); } } cout << ans << endl ; } return 0;}
hdu 4939 Stupid Tower Defense