二分查找

#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>

using namespace std;
const int N = 100010;

int n, day;

bool check(int num)//判断第一天吃掉num块巧克力是否可以
{
    int c = n;
    int d = day;
    int div = num;
    while(d) 
    {
        c -= div;
        d--;
        div = ceil((double)div / 2);
        if(c < 0)
            return false; //不可以
    }
    return true;//可以
}

int main()
{
    cin >> day >> n;
    int l = 1, r = n;
    while(l < r) //二分枚举
    {
        int mid = (l + r + 1) >> 1;
        if(!check(mid)) r = mid - 1;
        else l = mid;
    }
    cout << l << endl;
    return 0;
 }