标签:dp
Time Limit: 12000/6000 MS (Java/Others) Memory Limit:
131072/131072 K (Java/Others)
Problem Description
FSF is addicted to a stupid tower defense game. The goal of tower defense games is to try to stop enemies from crossing a map by building traps to slow them down and towers which shoot at them as they pass.
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.
Input
There are multiply test cases.
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)
Output
For each case, you should output "Case #C: " first, where C indicates the case number and counts from 1. Then output the answer. For each test only one line which have one integer, the answer to this question.
Sample Input
Sample Output
Case #1: 12
Hint
For the first sample, the first tower is blue tower, and the second is red tower. So, the total damage is 4*(1+2)=12 damage points.
题意:给出一条长为n个单位长度的直线,每通过一个单位长度需要t秒。
有3种塔,红塔可以在当前格子每秒造成x点伤害,绿塔可以在之后的格子每秒造成y点伤害,蓝塔可以使通过单位长度的时间增加z秒。问如何安排3种塔的顺序使得造成的伤害最大,输出最大伤害值。
分析:如果要安排红塔,则红塔在前面没有在后面造成的伤害大。所以可以枚举红塔的数量i,对前n-i座塔进行dp。
设dp[i][j]表示前i个单位长度中有j个蓝塔造成的最大伤害,则
dp[i][j] = max(dp[i-1][j-1] + (i - j) * y * (t + (j - 1) * z), dp[i-1][j] + (i - j - 1) * y * (t + j * z))
其中,(i - j) * y * (t + (j - 1) * z)表示i-j个绿塔在第i 个格子造成的伤害,(i - j - 1) * y * (t + j * z)表示i-j-1个绿塔在第i个格子造成的伤害。
求出dp[i][j]以后,则红塔数量为n-i时的总伤害为damage=dp[i][j] + (n - i) * x * (t + j * z) + (n - i) * (t + j * z) * (i - j) * y(后n-i个红塔造成的伤害加上前i-j个绿塔在后n-i个格子造成的伤害),所以最终的ans=max(ans, damage).
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 1505;
typedef __int64 LL;
LL dp[N][N];
int main()
{
LL x, y, z, t, n, i, j;
int T, cas = 0;
scanf("%d",&T);
while(T--)
{
scanf("%I64d%I64d%I64d%I64d%I64d",&n,&x,&y,&z,&t);
memset(dp, 0, sizeof(dp));
LL ans = n * t * x; //全部放红塔
for(i = 1; i <= n; i++) //前i个单位长度
{
for(j = 0; j <= i; j++) // 蓝塔数量
{
if(j == 0)
dp[i][j] = dp[i-1][j] + (i - j - 1) * y * t;
else
{
LL tmp1 = dp[i-1][j-1] + (i - j) * y * (t + (j - 1) * z); //第j个单位长度放蓝塔
LL tmp2 = dp[i-1][j] + (i - j - 1) * y * (t + j * z); //第j个单位长度不放蓝塔
dp[i][j] = max(tmp1, tmp2);
}
ans = max(ans, dp[i][j] + (n - i) * x * (t + j * z) + (n - i) * (t + j * z) * (i - j) * y);
}
}
printf("Case #%d: %I64d\n", ++cas, ans);
}
return 0;
}
hdu 4939 Stupid Tower Defense(DP)2014多校训练第7场,布布扣,bubuko.com
hdu 4939 Stupid Tower Defense(DP)2014多校训练第7场
标签:dp
原文地址:http://blog.csdn.net/lyhvoyage/article/details/38531575