An Easy Problem 优先队列/二分

链接：https://ac.nowcoder.com/acm/contest/33467/A
来源：牛客网

优先队列

先放入每个x坐标的最上面的值都优先队列中，然后取出队头，更新该x坐标的下一个值即可。

#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define int long long
#define fi first
#define se second
#define pb push_back

#define foa(x, y, z) for(int x = (y), ooo = (z); x <= z; ++x)
#define fos(x, y, z) for(int x = (y), ooo = (z); x >= z; --x)
#define ckmax(x, y) ((x) < (y) ? (x) = (y), 1 : 0)
#define ckmin(x, y) ((x) > (y) ? (x) = (y), 1 : 0)

typedef pair<int, int> pii;
typedef long long ll;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f3f3f3f3f;
const int N = 1e6 + 10;
int n, m;
vector<int> v;
int a[N];
void solve()
{
    int k;
    cin >> n >> m >> k;
    priority_queue<pii> q;
    foa(i, 1, n) q.push({i * m, i});
//     cout << q.top().fi << endl;
    
    foa(i, 1, k - 1) {
        auto t = q.top();
//         printf("%d \n", t.fi);
        q.pop();
        q.push({t.fi - t.se, t.se});
    }
    cout << q.top().fi << endl;
}
signed main()
{
	// ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    
	solve();
    return 0;
}

二分

二分一个值x，然后暴力计算出大于该值的数量，然后二分即可，注意二分值等于k-1时，右区间向mid的值逼近，不能搞反。

#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define int long long
#define fi first
#define se second
#define pb push_back

#define foa(x, y, z) for(int x = (y), ooo = (z); x <= z; ++x)
#define fos(x, y, z) for(int x = (y), ooo = (z); x >= z; --x)
#define ckmax(x, y) ((x) < (y) ? (x) = (y), 1 : 0)
#define ckmin(x, y) ((x) > (y) ? (x) = (y), 1 : 0)

typedef pair<int, int> pii;
typedef long long ll;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f3f3f3f3f;
const int N = 1e6 + 10;
int n, m;
vector<int> v;
int a[N];
// > x num
int gt(int x)
{
    int ans = 0;
    foa(i, 1, n)
        ans += max(m - x / i, 0ll);
    return ans;
}
void solve()
{
    int k;
    cin >> n >> m >> k;
    int l = 0, r = 1e13;
    while(l < r) {
        int mid = (l + r) >> 1;
        if(gt(mid) <= k - 1) r = mid;
        else l = mid + 1;
    }
    cout << l << endl;
}
signed main()
{
	// ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    
	solve();
    return 0;
}