hihoCoder #1269 : 优化延迟 【二分 + 优先队列】

题目链接：hihoCoder #1269 : 优化延迟

思路：二分然后维护一个 priorityqueue 就 O 了。

AC 代码：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define PI acos(-1.0)
#define CLR(a, b) memset(a, (b), sizeof(a))
#define fi first
#define se second
using namespace std;
typedef long long LL;
typedef pair<int, int> pii;
const int MAXN = 1e5+10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
void getmax(int &a, int b) {a = max(a, b); }
void getmin(int &a, int b) {a = min(a, b); }
void add(LL &x, LL y) { x += y; x %= MOD; }
priority_queue<int, vector<int>, less<int> > Q;
int N; LL S;
int a[MAXN];
LL Count(int o)
{
    LL ans = 0;
    int i = 1, j = 1;
    while(i <= N)
    {
        while(Q.size() < o && i <= N) {
            Q.push(a[i]), i++;
        }
        int v = Q.top(); Q.pop();
        ans += 1LL * v * j; j++;
    }
    while(!Q.empty())
    {
        int v = Q.top(); Q.pop();
        ans += 1LL * v * j; j++;
    }
    return ans;
}
int main()
{
    while(scanf("%d%lld", &N, &S) != EOF)
    {
        for(int i = 1; i <= N; i++) scanf("%d", &a[i]);
        int l = 1, r = N;
        int ans = -1;
        while(r >= l)
        {
            int mid = (l + r) >> 1;
            if(Count(mid) <= S)
            {
                ans = mid;
                r = mid-1;
            }
            else
                l = mid+1;
        }
        cout << ans << endl;
    }
    return 0;
}