每日一题 - 240320 - 付账问题

• 付账问题

---

• TAG - $芝士水题、算法-【贪心】$
• 时间复杂度 - $O(N)$

//
#include <bits/stdc++.h>
using namespace std;
#define int long long   // N * 1e9 > int

const int N = 5e5 + 6;
int a[N];

void solve() {
    int n, s;
    scanf("%lld%lld", &n, &s);
    for (int i = 1; i <= n; i++) scanf("%lld", &a[i]);

    sort(a + 1, a + n + 1);

    double avg = (double)s / n;

    double sum = 0;
    for (int i = 1; i <= n; i++) {
        // (1) 钱不够 avg = s / n
        // (2) 钱不够 now_avg = s / (n - i + 1)
        if (a[i] * (n - i + 1) < s) {
            sum += (avg - a[i]) * (avg - a[i]);
            s -= a[i];
        } else {
          // (3) 钱足够
            double now_avg = (double)s / (n - i + 1);
            sum += (now_avg - avg) * (now_avg - avg) * (n - i + 1);
            break;
        }
    }
    printf("%.4lf\n", sqrt(sum / n));
}

signed main() {
    int t = 1;
    // scanf("%d", &t);
    while (t--) solve();
    return 0;
}

---

实现细节

• 爆 int

---

参考示意图

• `

---

参考链接

• `

---

作者 | 乐意奥AI