【二分答案】CF1613 C. Poisoned Dagger

题目：Problem - C - Codeforces

本题的优解是二分答案，但我其实不会二分，本质是用了两个指针作为边界，然后不断对半缩小范围来快速确定答案。

神奇的二分法

代码：

#include <iostream>
using namespace std;
typedef long long ll;
ll a[110];
ll n, h;
bool check(ll k)
{
    ll t = h - k;
    for (int i = 2; i <= n; ++i)
    {
        t -= min(k, a[i] - a[i - 1]);
    }
    if (t <= 0)
        return 1;
    else
        return 0;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T;
    cin >> T;
    while (T--)
    {
        cin >> n >> h;
        for (int i = 1; i <= n; ++i)
        {
            cin >> a[i];
        }
        ll l = 1, r = h;
        while (l <= r)
        {
            ll mid = (l + r) >> 1;//取中点
            if (check(mid))
            {
                r = mid - 1;
            }
            else
                l = mid + 1;
        }
        cout << l << endl;
    }
    return 0;
}