題目

 Once upon a time, in the Kingdom of Loowater, a minor nuisance turned into a major problem. The shores of Rellau Creek in central Loowater had always been a prime breeding ground for geese. Due to the lack of predators, the geese population was out of control. The people of Loowater mostly kept clear of the geese. Occasionally, a goose would attack one of the people, and perhaps bite off a finger or two, but in general, the people tolerated the geese as a minor nuisance. One day, a freak mutation occurred, and one of the geese spawned a multi-headed fire-breathing dragon. When the dragon grew up, he threatened to burn the Kingdom of Loowater to a crisp. Loowater had a major problem. The king was alarmed, and called on his knights to slay the dragon and save the kingdom. The knights explained: “To slay the dragon, we must chop off all its heads. Each knight can chop off one of the dragon’s heads. The heads of the dragon are of different sizes. In order to chop off a head, a knight must be at least as tall as the diameter of the head. The knights’ union demands that for chopping off a head, a knight must be paid a wage equal to one gold coin for each centimetre of the knight’s height.” Would there be enough knights to defeat the dragon? The king called on his advisors to help him decide how many and which knights to hire. After having lost a lot of money building Mir Park, the king wanted to minimize the expense of slaying the dragon. As one of the advisors, your job was to help the king. You took it very seriously: if you failed, you and the whole kingdom would be burnt to a crisp! Input The input contains several test cases. The first line of each test case contains two integers between 1 and 20000 inclusive, indicating the number n of heads that the dragon has, and the number m of knights in the kingdom. The next n lines each contain an integer, and give the diameters of the dragon’s heads, in centimetres. The following m lines each contain an integer, and specify the heights of the knights of Loowater, also in centimetres. The last test case is followed by a line containing ‘0 0’. Output For each test case, output a line containing the minimum number of gold coins that the king needs to pay to slay the dragon. If it is not possible for the knights of Loowater to slay the dragon, output the line ‘Loowater is doomed!’. Sample Input 2 3 5 4 7 8 4 2 1 5 5 10 0 0 Sample Output 11 Loowater is doomed!

題目大意

 有一條惡龍，他有n個頭，有m個騎士。

每個騎士只能砍死惡龍的一個頭，而且只有騎士的身高大於惡龍偷得直徑的時候才能將其砍死。

騎士將惡龍砍死，需要向騎士支付等同於騎士身高的金幣

無限個測試樣例，輸入0 0結束測試

首先輸入 n m

然後輸入n個惡龍頭的直徑  輸入m個騎士的身高

判斷是否能夠將惡龍砍死，如果能砍死，輸出所需支付的最小金幣

如果不能 輸出Loowater is doomed!

演算法： 貪心

程式碼 

#include <iostream>
#include <algorithm>
using namespace std;
int a[20005],b[20005];  //a惡龍 b騎士 
int main()
{
	int n,m,i,j;
	while(cin>>n>>m)
	{
		if(n==0 && m==0) break;
		for(i=0;i<n;i++)
		{
			cin>>a[i];
		}	
		for(i=0;i<m;i++)
		{
			cin>>b[i];
		}
		sort(a,a+n);
		sort(b,b+m);
		int ans=0,num=0,st=0;
		for(i=0;i<n;i++) 
			for(j=st;j<m;j++)      //j要從st開始，st代表現在判斷到哪一個騎士了
			{
				if(b[j]>=a[i])    //只有升高大於等於直徑才能滿足要求
				{
					ans+=b[j];     //金幣值
					num++;         //num用來判斷砍死多少個頭
					st=j+1;        //st用來標記 接下來要判斷哪一個騎士
					break;
				} 
			}
		if(num<n) cout<<"Loowater is doomed!"<<endl;
		else cout<<ans<<endl;
	}
	return 0;
}
 

 解析

要求最小金幣，那麼肯定是要有限使用花費少的騎士（也就是身高小的）

將身高和半徑排序

從小的開始匹配

也就是貪心