POJ 3040 Allowance(贪心经典题目）

#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
struct node
{
int x, y;
}cow[21];
bool cmp(node a, node b)
{
return a.x < b.x;
}
int main()
{
int N, C;
while (cin >> N >> C)
{
int sum = 0, used[21];
memset(used, 0, sizeof(used));
int i, j;
for (i = 0, j = 0; i < N; i++)
{
int a, b; cin >> a >> b;
if (a >= C) sum = sum + b;
else
{
cow[j].x = a;
cow[j++].y = b;
}
}
sort(cow, cow + j, cmp);
while (1)
{
int s = C,temp=0;
for (i = j - 1; i >= 0; i--)
{
if (s > 0&&cow[i].y>0)
{
temp = min(cow[i].y, s / cow[i].x);
used[i] += temp;
s = s - temp*cow[i].x;
}
}
if (s > 0)
{
for (i = 0; i < j; i++)
{
if (used[i] < cow[i].y&&cow[i].x>=s)
{
used[i]++;
s = s - cow[i].x; break;
}
}
}
if (s > 0) break;
sum++;
for (i = 0; i < j; i++)
{
cow[i].y -= used[i];
used[<
cf83
/span>i] = 0;
}
}
cout << sum << endl;
}
return 0;
}