NEUOJ1207 Birthday present (簡單數學)

題目鏈接

2017ICPCECIC北方邀請賽D題

代碼

#include <iostream>
#include <cstdio>
#include <cstring>
const int INF=0x3f3f3f3f;
const int MAXN=1000010;
using namespace std;
int p[MAXN];
int main()
{
    int n,k,i,mina,ans,low,high,cnt,l,r,t;
    while (scanf("%d%d",&n,&k)!=EOF)
    {
        mina=INF;
        low=INF;high=0;
        memset(p,0,sizeof(p));
        for (i=1;i<=n;i++)
        {
            scanf("%d",&t);
            mina=min(mina,t);
            low=min(low,t);
            high=max(high,t);
            p[t]++;
        }
        if (mina<=k+1)
        {
            printf("%d\n",mina);
            continue;
        }
        else
        {
            for (i=1;i<=high;i++)
                p[i]+=p[i-1];        ///p[i]表示a[]中小於等於i的數量
            for (ans=high;ans>k+1;ans--)
            {
                cnt=0;
                for (i=0;i<=high;i+=ans)
                {
                    l=i-1>=0?p[i-1]:0;
                    r=i+k<=high?p[i+k]:n;
                    cnt+=(r-l);
                }
                if (cnt==n) break;
            }
            printf("%d\n",ans);
        }
    }
    return 0;
}