zoj3623 Battle Ships

Posted ljbguanli

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了zoj3623 Battle Ships相关的知识,希望对你有一定的参考价值。

Battle Ships is a new game which is similar to Star Craft. In this game, the enemy builds a defense tower, which has L longevity. The player has a military factory, which can produce N kinds of battle ships. The factory takes ti seconds to produce the i-th battle ship and this battle ship can make the tower loss li longevity every second when it has been produced. If the longevity of the tower lower than or equal to 0, the player wins. Notice that at each time, the factory can choose only one kind of battle ships to produce or do nothing. And producing more than one battle ships of the same kind is acceptable.

Your job is to find out the minimum time the player should spend to win the game.

Input

There are multiple test cases. 
The first line of each case contains two integers N(1 ≤ N ≤ 30) and L(1 ≤ L ≤ 330), N is the number of the kinds of Battle Ships, L is the longevity of the Defense Tower. Then the following N lines, each line contains two integers i(1 ≤ i ≤ 20) and li(1 ≤ li ≤ 330) indicating the produce time and the lethality of the i-th kind Battle Ships.

Output

Output one line for each test case. An integer indicating the minimum time the player should spend to win the game.

Sample Input

1 1
1 1
2 10
1 1
2 5
3 100
1 10
3 20
10 100

Sample Output

2
4
5
这题比較难想到,看了题解后才恍然大悟。。

这里把时间看做容量,所打怪物的血为价值。用dp[j]表示j这个时候最多能打怪物的血量,那么利用全然背包能够得到dp[j]=max(dp[j],dp[j-t[i]]+(j-t[i])*l[i]),当中dp[j-t[i]]是由于刚開始制造要花t[i]时间,后面指的是制造出来后的每一秒能够打多少血。

#include<stdio.h>
#include<string.h>
int max(int a,int b){
	return a>b?

a:b; } int dp[500]; int main() { int n,m=490,last,i,j; int t[50],l[50]; while(scanf("%d%d",&n,&last)!=EOF) { for(i=1;i<=n;i++){ scanf("%d%d",&t[i],&l[i]); } memset(dp,0,sizeof(dp)); for(i=1;i<=n;i++){ for(j=t[i];j<=m;j++){ dp[j]=max(dp[j],dp[j-t[i]]+(j-t[i])*l[i]); } } for(i=1;i<=m;i++){ if(dp[i]>=last){ printf("%d\n",i);break; } } } return 0; }




以上是关于zoj3623 Battle Ships的主要内容,如果未能解决你的问题,请参考以下文章

HDU - 5093 Battle ships

CodeForces - 567D One-Dimensional Battle Ships

[HDOJ5093] Battle ships(最大匹配)

Battle ships HDU - 5093二分匹配

51 nod 1521 一维战舰 时间复杂度O(n),同 Codeforces 567D. One-Dimensional Battle Ships 有详细注释

UVA 322 ships (POJ 1138)