Polycarp invited all his friends to the tea party to celebrate the holiday. He has n cups, one for each of his n friends, with volumes a1, a2, ..., an. His teapot stores w milliliters of tea (w ≤ a1 + a2 + ... + an). Polycarp wants to pour tea in cups in such a way that:
- Every cup will contain tea for at least half of its volume
- Every cup will contain integer number of milliliters of tea
- All the tea from the teapot will be poured into cups
- All friends will be satisfied.
Friend with cup i won't be satisfied, if there exists such cup j that cup i contains less tea than cup j but ai > aj.
For each cup output how many milliliters of tea should be poured in it. If it's impossible to pour all the tea and satisfy all conditions then output -1.
The first line contains two integer numbers n and w (1 ≤ n ≤ 100,
).
The second line contains n numbers a1, a2, ..., an (1 ≤ ai ≤ 100).
Output how many milliliters of tea every cup should contain. If there are multiple answers, print any of them.
If it's impossible to pour all the tea and satisfy all conditions then output -1.
2 10 8 7
6 4
4 4 1 1 1 1
1 1 1 1
3 10 9 8 10
-1
In the third example you should pour to the first cup at least 5 milliliters, to the second one at least 4, to the third one at least 5. It sums up to 14, which is greater than 10 milliliters available.
首先对杯子按照容量排序,首先每个杯子分别刚好到(m+1)/2毫升的水,这样可以保证大于一半而且是整数,然后如果水不够,说明不可能,如果水多了,则从最后一个开始,往前依次加满。如果每个杯子都满了水还是没用完也不行。
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <iomanip>
using namespace std;
#define _ ios::sync_with_stdio(false)
const int MAXN = 110;
const int INF=0x7fffffff;
int n;
struct cup{
int num;
int m;
int t;
}a[MAXN];
int cmp(cup x,cup y){
return x.m<y.m;
}
int cc(cup x,cup y){
return x.num<y.num;
}
int main(){
int w;
scanf("%d%d",&n,&w);
for(int i=1;i<=n;i++){
scanf("%d",&a[i].m);
a[i].num=i;
}
int MAX=0;
int ok=1;
sort(a+1,a+n+1,cmp);
for(int i=1;i<=n;i++){
int x=(a[i].m+1)/2;
//cout<<x<<endl;
if(w<x){
ok=0;
break;
}
if(i==n){
x=w;
if(a[i].m<x){
w-=(a[i].m-a[i].t);
a[i].t=a[i].m;
for(int j=n-1;j>=1;j--){
int y=a[j].m;
y=min(w+a[j].t,y);
w-=(y-a[j].t);
a[j].t=y;
if(w<=0)
break;
}
if(w>0){
ok=0;
break;
}
}else{
a[i].t=x;
}
}
if(i!=n)
a[i].t=x;
w-=x;
}
if(!ok){
puts("-1");
return 0;
}
sort(a+1, a+n+1, cc);
for(int i=1;i<=n;i++){
printf("%d%c",a[i].t,i==n?'\n':' ');
}
}

本文介绍了一种解决茶话会上如何公平分配有限茶水量的算法。该算法确保每位参与者至少获得其杯子容量一半的茶水,且水量为整数。通过排序与逐步填充策略,实现了条件下的最优解。
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