题解 | #机器人跳跃问题#

#include<bits/stdc++.h>
#define endl '\n'
#define all(x) x.begin(), x.end()
#define all_(x) x.begin() + 1, x.end()

using namespace std;
using ll = long long;
using vi = vector<int>;

int main() {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	int n; cin >> n;
    vi vt(n);
    for(int &x : vt) cin >> x;
    ll l = 0, r = *max_element(all(vt));
    ll m = r;
	// 左右开区间写法
    auto check = [&](ll start) -> bool {
        for(int &x : vt) {
            start += start - x;
            if(start < 0) return false;
            else if(start >= m) return true;
        }
        return true;
    };
	// 二分答案
    while(r > l + 1) {
        ll mid = (l + r) >> 1;
        ((check(mid)) ? r : l) = mid;
    }

    cout << r << endl;
	return 0;
}