2020-09-08 [USACO1.3]混合牛奶 Mixin

https://www.luogu.com.cn/problem/P1208

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <sstream>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;

template<typename DataType>
DataType qmi(DataType m, int k)
{
    DataType res = 1, t = m;
    while (k)
    {
        if (k&1) res = res * t;
        t = t * t;
        k >>= 1;
    }
    return res;
}

int read(){
    int x = 0,f = 1;
    char c = getchar();
    while (c<'0'||c>'9') {
        if (c=='-') {
            f = -1;
        }
        c = getchar();
    }
    while (c>='0'&&c<='9') {
        x = x*10+c-'0';
        c = getchar();
    }
    return x*f;
}

#define fi(a,b) for(int i = a; i <= b; i++)
#define fj(a,b) for(int j = a; j >= b; j--)

struct priceAndCnt{
    int price,cnt;
};

void quickSort(priceAndCnt *a,int left,int right){
    int i,j;
    
    priceAndCnt temp,t;
    
    temp = a[(left+right)/2];//基准值
    
    i = left;
    j = right;
    
    while(i<=j){
        while (a[j].price > temp.price) {
            j--;
        }
        
        while (a[i].price < temp.price) {
            i++;
        }
        
        if (i<=j) {
            t = a[i];
            a[i] = a[j];
            a[j] = t;
            //继续下一步
            i++;
            j--;
        }
    }
    
    if(left<j)quickSort(a,left, j);//继续分治
    if(i<right)quickSort(a,i, right);//继续分治
}

int m,n,ans = 0;
priceAndCnt arr[2000005];
int main(){
    //输入部分
    n = read();
    m = read();
    fi(1, m){
        arr[i].price = read();
        arr[i].cnt = read();
    }
    
    //排序，然后一一匹配
    quickSort(arr, 1, m);
    
//    fi(1, m){
//        cout<<arr[i].price<<"\t"<<arr[i].cnt<<endl;
//    }
    fi(1, m){
        while(n && arr[i].cnt){
            n --;
            arr[i].cnt --;
            ans += arr[i].price;
        }
    }
    cout<<ans;
}
/*
100 5
5 20
9 40
3 10
8 80
6 30
============
6
*/