AtCoder Beginner Contest 174

第一次 ak ABC，纪念一下。

比赛链接：https://atcoder.jp/contests/abc174

A - Air Conditioner

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n; cin >> n;
    cout << (n >= 30 ? "Yes" : "No");
}

B - Distance

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n, d; cin >> n >> d;
    int cnt = 0;
    for (int i = 0; i < n; i++) {
        int x, y; cin >> x >> y;
        if (1ll * x * x + 1ll * y * y <= 1ll * d * d) ++cnt;
    }
    cout << cnt << "\n";
}

C - Repsept

#include <bits/stdc++.h>
using namespace std;
int main() {
    int k; cin >> k;
    int ans = 1;
    for (int mod = 7; mod % k; mod = (mod * 10 + 7) % k)
        if (++ans > k) { ans = -1; break; }
    cout << ans << "\n";
}

D - Alter Altar

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n; string s; cin >> n >> s;
    int ans = 0;
    int l = 0, r = n - 1;
    while (l < r) {
        if (s[l] == 'W') {
            while (r > l and s[r] != 'R') --r;
            if (r > l) {
                ++ans;
                ++l;
                --r;
            }
        } else ++l;
    }
    cout << ans << "\n";
}

E - Logs

#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 100;

int n, k;
int a[N];

bool ok(int mid) {
    int need = 0;
    for (int i = 0; i < n; i++) {
        need += (a[i] - 1) / mid;
    }
    return need <= k;
}

int main() {
    cin >> n >> k;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    int l = 1, r = 1e9;
    while (r - l > 1) {
        int mid = (l + r) / 2;
        if (ok(mid)) r = mid;
        else l = mid;
    }
    cout << (ok(l) ? l : r) << "\n";
}

F - Range Set Query

原题P1972。

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 100;

int a[N], bit[N], vis[N], ans[N];

struct P{
    int l, r, pos;
}p[N];

void add(int pos, int val) {
    for (int i = pos; i <= N; i += i & (-i)) {
        bit[i] += val;
    }
}

int sum(int pos) {
    int ans = 0;
    for (int i = pos; i != 0; i -= i & (-i)) {
        ans += bit[i];
    }
    return ans;
}

int main() {
    int n, m; cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    for (int i = 1; i <= m; i++) {
        cin >> p[i].l >> p[i].r;
        p[i].pos = i;
    }
    sort(p + 1, p + 1 + m, [&] (P x, P y) {
        return x.r < y.r;
    });
    int r = 1;
    for (int i = 1; i <= m; i++) {
        for (int j = r; j <= p[i].r; j++) {
            if (vis[a[j]]) add(vis[a[j]], -1);
            add(j, 1);
            vis[a[j]] = j;
        }
        r = p[i].r + 1;
        ans[p[i].pos] = sum(p[i].r) - sum(p[i].l - 1);
    }
    for (int i = 1; i <= m; i++) {
        cout << ans[i] << "\n";
    }
}