蓝桥杯2022青蛙过河_二分枚举

P2026 - [蓝桥杯2022初赛] 青蛙过河 - New Online Judgehttp://oj.ecustacm.cn/problem.php?id=2026二分枚举y，检查每一段长度为y的区间内的石头高度总和是否>=2x。

如果有一段长度为y的区间不能被经过2x次，那么肯定不行。

#include 
using namespace std;
typedef long long ll;
const int N = 1e5 + 4;
ll sum[N] = {0};
int n, x;
int check(int y) {
    for (int i = y; i <= n - 1; i++) {
        if (sum[i] - sum[i - y] < 2 * x) {
            return 0;
        }
    }
    return 1;
}
int main() {
    cin >> n >> x;
    int h;
    for (int i = 1; i <= n - 1; i++) {
        cin >> h;
        sum[i] = sum[i - 1] + h;
    }
    int left = 0, right = 1e5;
    while (left < right) {
        int mid = (left + right) >> 1;
        if (check(mid)) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
    cout << left;
    return 0;
}