AtCoder Contest 229-C-Cheese

Problem Statement

Takahashi, who works for a pizza restaurant, is making a delicious cheese pizza for staff meals.
There are NN kinds of cheese in front of him.
The deliciousness of the ii-th kind of cheese is A_iAi per gram, and B_iBi grams of this cheese are available.
The deliciousness of the pizza will be the total deliciousness of cheese he puts on top of the pizza.
However, using too much cheese would make his boss angry, so the pizza can have at most WW grams of cheese on top of it.
Under this condition, find the maximum possible deliciousness of the pizza.

Constraints

All values in input are integers.

1 \le N \le 3 \times 10^51≤N≤3×105

1 \le W \le 3 \times 10^81≤W≤3×108

1 \le A_i \le 10^91≤Ai≤109

1 \le B_i \le 10001≤Bi≤1000

Input

Input is given from Standard Input in the following format:
NN WW
A_1A1 B_1B1
A_2A2 B_2B2
\vdots⋮
A_NAN B_NBN
Output

Print the answer as an integer.

Sample Input 1 Copy

Copy
3 5
3 1
4 2
2 3
Sample Output 1 Copy

Copy
15
The optimal choice is to use 11 gram of cheese of the first kind, 22 grams of the second kind, and 22 grams of the third kind.
The pizza will have a deliciousness of 1515.

Sample Input 2 Copy

Copy
4 100
6 2
1 5
3 9
8 7
Sample Output 2 Copy

Copy
100
There may be less than WW grams of cheese in total.

Sample Input 3 Copy

Copy
10 3141
314944731 649
140276783 228
578012421 809
878510647 519
925326537 943
337666726 611
879137070 306
87808915 39
756059990 244
228622672 291
Sample Output 3 Copy

Copy
2357689932073

题目类型：贪心

题目目标：寻找Wgram内N种芝士可以组合出最大的美味度

注意点：注意一下数据范围，3+5+9 = 17， 10e17 ，long long

解题思路：1）一开始认为是容量为1的多重背包，然后RE了

2）后来发现有更简单的方法；

1）每种芝士只有数量和美味度两种性质，pair就可以了。读入。

2）排序，自己写cmp也可以，sort+reverse()也可以。

3）在容量允许的情况下，把当前美味度最大的芝士全放入，若容量不够，把剩余的容量都用来放当前美味度最大的芝士。容量为0，跳出输出。

AC代码：

#include  <bits/stdc++.h>
#define rep(x, a, b) for(int x=a; x<=b; x++)
#define inf 0x3f3f3f3f
#define ll long long
using namespace std;
const int N= 3e5+10;
int n, w;
bool cmp(pair< ll, ll > a, pair< ll, ll > b)
{return a.first > b.first;
}
int main()
{ll ans = 0;scanf("%d%d", &n,&w);vector< pair< ll, ll > > v(n);rep(i, 0, n-1)cin>>v[i].first>>v[i].second;sort(v.begin(), v.end(), cmp);rep(i, 0, n-1){if(!w) break;if(w - v[i].second >= 0){w -= v[i].second;ans += v[i].first*v[i].second;}else if(w < v[i].second){ans += v[i].first*w;w = 0;}}cout<<ans;return 0;
}

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AtCoder Contest 229-C-Cheese

Problem Statement

Constraints

Input

Output

Sample Input 1 Copy

Sample Output 1 Copy

Sample Input 2 Copy

Sample Output 2 Copy

Sample Input 3 Copy

Sample Output 3 Copy

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