51nod1420 数袋鼠好有趣

排序后二分

#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;

const int maxn = 1e6 + 50;
int a[maxn];
int s = 0;
int maxi = 0;
int n;

int judge(int k){
    for(int i = 1, j = k + 1; i <= k; i++, j++){
        for(; a[j] < 2 * a[i] && j <= n; ) j++;
        if(j > n) return 0;
    }
    return 1;
}

int main(){ 
    scanf("%d", &n);
    int l = 1, r = n, ans = 0;
    for(int i = 1; i <= n; i++){
        scanf("%d", &a[i]);
    }
    sort(a + 1, a + 1 + n);
    while(l <= r){
        int mid = (l + r) >> 1;
        if(judge(mid)){
            ans = mid;
            l = mid + 1;
        }else r = mid - 1;
    }
    printf("%d\n", n - ans);
    return 0;
}