Crixalis‘s Equipment

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Problem Description

Crixalis - Sand King used to be a giant scorpion(蝎子) in the deserts of Kalimdor. Though he‘s a guardian of Lich King now, he keeps the living habit of a scorpion
like living underground and digging holes.

Someday Crixalis decides to move to another nice place and build a new house for himself (Actually it‘s just a new hole). As he collected a lot of equipment, he needs to dig a hole beside his new house to store them. This hole has a volume of V units, and Crixalis
has N equipment, each of them needs Ai units of space. When dragging his equipment into the hole, Crixalis finds that he needs more space to ensure everything is placed well. Actually, the ith equipment needs Bi units of space during the moving. More precisely
Crixalis can not move equipment into the hole unless there are Bi units of space left. After it moved in, the volume of the hole will decrease by Ai. Crixalis wonders if he can move all his equipment into the new hole and he turns to you for help.

Input

The first line contains an integer T, indicating the number of test cases. Then follows T cases, each one contains N + 1 lines. The first line contains 2 integers: V, volume of a hole and N, number of equipment respectively. The next
N lines contain N pairs of integers: Ai and Bi.

0<T<= 10, 0<V<10000, 0<N<1000, 0 <Ai< V, Ai <= Bi < 1000.

Output

For each case output "Yes" if Crixalis can move all his equipment into the new hole or else output "No".

Sample Input

2

20 3
10 20
3 10
1 7

10 2
1 10
2 11

Sample Output

Yes
No

分析：

该题讲的是搬家问题，搬运东西需要占多大空间还有搬运时要求的空间。该题的贪心原则则是尽可能的装入东西，即

           停放体积 移动体积

将N件物品按照b1-a1>b2-a2进行排序 然后依次放入洞中，即按照差值从大到小放入洞中

#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;

struct node
{
	int a,b,c;
}s[1005];

int cmp(node x,node y)
{
	return x.c>y.c;
}

int main()
{
	int T;
	cin>>T;
	while(T--)
	{
		int n,m;
		cin>>n>>m;
		int i,flag=0;;
		for(i=0;i<m;i++)
		{
			cin>>s[i].a>>s[i].b;
			s[i].c=s[i].b-s[i].a;
		}

		sort(s,s+m,cmp);
		for(i=0;i<m;i++)
		{
			if(n>=s[i].b)   n-=s[i].a;
			else
			{
				flag=1;
				break;
			}
		}

		if(flag)
			cout<<"No\n";
		else
			cout<<"Yes\n";
	}

	return 0;
}

HDUJ 3177 Crixalis's Equipment 贪心