Usaco Section1.3 Mixing Milk Problem Solving report

Milk Problem Solving Report--icedream61 Blog Park (reproduced please specify the source)
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Topic
I am a milk manufacturer, I need n gallons of milk a day, and a total of M farmers can supply me.
This m farmer's information is a total of M-line, the first farmer has num[i] gallon milk, the price per gallon is price[i].
Ask me to buy enough milk for the minimum amount of money needed.
The data guarantee that the total amount of milk produced by farmers must be adequate.
"Data Range"
0<=n<=2,000,000
0<=m<=5,000
0<=price[i]<=1,000
0<=num[i]<=2,000,000
"Input Sample"
100 5
5 20
9 40
3 10
8 80
6 30
"Output Example"
630
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Analysis
Sort it out and be greedy.
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Summary
Once again AC.
Incidentally, the following class is reviewed for the operation symbol overloading.

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Code

1 /*2 id:icedrea13 Prob:milk4 lang:c++5 */6 7#include <iostream>8#include <fstream>9 using namespacestd;Ten  One Const intMAXN =2000000; A Const intMAXM = the; -  - structFarmer the { -     intPrice ; -     intnum; -FriendBOOL operator< (FarmerConst&x,farmerConst&y) {returnx.price<Y.price;} + }; -  + intn,m; AFarmer f[1+MAXM]; at  - voidQsortintLintR) - { -     if(L&GT;=R)return; -     inti=l,j=R; -Farmer x=f[(l+r) >>1]; in      while(true) -     { to          while(f[i]<x) + +i; +          while(X<f[j])--J; -         if(I&GT;J) Break; the swap (f[i],f[j]); *++i; --J; $     }Panax Notoginseng qsort (L,J); qsort (i,r); - } the  + intMain () A { theIfstreaminch("milk.in"); +Ofstream out("Milk.out"); -  $     inch>>N>>M; $      for(intI=1; i<=m;++i)inch>>F[i].price>>F[i].num; -  -Qsort1, M); the  -     intcost=0;Wuyi      for(intI=1; N && i<=m;++i) the     { -         intnum=min (n,f[i].num); WuN-=num; cost+=f[i].price*num; -     } About      out<<cost<<Endl; $  -     inch. Close (); -      out. Close (); -     return 0; A}

Usaco Section1.3 Mixing Milk Problem Solving report