难点在于防止数据溢出

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 1e5 + 10;
int a[N], maxn, n;

bool check(int x)
{
    for (int i = 0; i < n; i ++ )
    {
        x = x * 2 - a[i];
        if (x >= maxn) return true; // 只要大于数组中的最大元素，就会一直单增
        if (x < 0)  return false;
    }

    return true;
}


int main()  
{
    scanf("%d", &n);
    int mid;

    for (int i = 0; i < n; i ++ )
    {
        scanf("%d", &a[i]);
        if (a[i] > maxn) maxn = a[i];
    }


    int l = 1, r = 1e5;

    while (l < r)
    {
        mid = l + r >> 1;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }

    printf("%d", l);

    return 0;
}