HDU 3530 Subsequence

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;int a[1000005],id1[1000005],id2[1000005];int main(){    int i,j,n,m,k;    while(scanf("%d %d %d",&n,&m,&k)!=EOF)    {        for(i=0;i<n;i++)            scanf("%d",&a[i]);        int first1=0,last1=0,first2=0,last2=0;        int ans=0,now=0;        for(i=0;i<n;i++)        {            while(first1<last1&&a[id1[last1-1]]>a[i]) last1--;id1[last1++]=i;            while(first2<last2&&a[id2[last2-1]]<a[i]) last2--;id2[last2++]=i;            while(first1<last1&&first2<last2&&(a[id2[first2]]-a[id1[first1]]>k))            {                if(id1[first1]<id2[first2]) {now=id1[first1]+1;first1++;}                else {now=id2[first2]+1;first2++;}                //printf("mm\n");            }            if(a[id2[first2]]-a[id1[first1]]<=k&&a[id2[first2]]-a[id1[first1]]>=m)                ans=max(ans,i-now+1);        }        printf("%d\n",ans);    }    return 0;}