HDU6047 Maximum Sequence（树状数组）

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <iostream>using namespace std;/*树状数组求区间最值*/const int maxn=250000+5;const int mod=1e9+7;typedef long long int ll;ll ans;int n,m;int a[maxn*2],b[maxn*2],c[maxn*2],h[maxn*2];int lowbit(int x){    return x & (-x);}void update(int x){    int lx,i;    while(x<=2*n)    {        h[x]=a[x];        lx=lowbit(x);        for(i=1;i<lx;i<<=1)            h[x]=max(h[x],h[x-i]);        x+=lowbit(x);    }}int query(int x, int y){    int ans = 0;    while (y >= x)    {        ans = max(a[y], ans);        y --;        for (; y-lowbit(y) >= x; y -= lowbit(y))            ans = max(h[y], ans);    }    return ans;}int main(){    while(~scanf("%d",&n))    {        ans=0;        ll maxv=0;        memset(a,0,sizeof(a));        memset(b,0,sizeof(b));        memset(c,0,sizeof(c));        memset(h,0,sizeof(h));        for(int i=1;i<=n;i++)        {            scanf("%d",&c[i]);            a[i]=c[i]-i;        }        for(int i=1;i<=n;i++)        {            scanf("%d",&b[i]);        }        sort(b+1,b+1+n);        for(int i=1;i<=2*n;i++)        {            update(i);        }        for(int i=n+1;i<=2*n;i++)        {            int ql=b[i-n];            maxv=query(ql,i);            ans=(ans+maxv)%mod;            a[i]=maxv-i;            update(i);        }        printf("%lld\n",ans);    }    return 0;}