2020-09-17 砍树

https://www.luogu.com.cn/problem/P1873

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <sstream>
#include <algorithm>
#include <cstring>
#include <vector>
#include <queue>
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 qmi(int m, int k)
{
    int 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 fie(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 n;
long long m;
long long lef,rig = 0;
long long mid;//看上面的解释啊
int total,tim;//这个不用管，后面会提到的

bool Judge(long long x,long long * a)
{
    long long ans = 0;
    fie(1,n){//这里大家应该看得出，是在用贪心来看一看这个最大值是否能为x
        long long t = a[i] - x;
        if (t > 0) {
            ans += t;
        }
    }
    
    return ans < m;//返回结果}
}

int main()
{
    cin>>n>>m;
    
    long long a[n];
    
    fie(1, n){
        cin>>a[i];
        rig=max(rig,a[i]);//找到最长木材
    }
    
    lef = 0;
    while (lef <= rig){//非递归式二分正常向写法，可理解为一般框架
        mid = (lef + rig) / 2;//这再看不出是啥意思可以退群了
        if ( Judge(mid,a) ){//是否小了
            rig = mid - 1;
        } else {
            lef = mid + 1;
        }
    }
    cout<<lef - 1<<endl;
    return 0;
}
/*
5 20
4 42 40 26 46
============
36
*/