HDU 4262

线段树记录区间中已取走的个数

#include<cstdio>#include<cstring>#include<algorithm>#define N 100100using namespace std;int n;int now;long long ans;int a[N],pos[N];struct Tree{    int l,r,num;}tree[N*3];void build(int s,int t,int id){    tree[id].l=s,tree[id].r=t,tree[id].num=0;    if(s!=t){        int mid=(s+t)>>1;        build(s,mid,id<<1);        build(mid+1,t,id<<1|1);    }}void insert(int pos,int id){    tree[id].num++;    if(tree[id].l==tree[id].r)        return;    int mid=(tree[id].l+tree[id].r)>>1;    if(pos<=mid)insert(pos,id<<1);    else insert(pos,id<<1|1);}int query(int s,int t,int id){    if(tree[id].l==s && tree[id].r==t)        return tree[id].num;    int mid=(tree[id].l+tree[id].r)>>1;    if(mid>=t)return query(s,t,id<<1);    else if(mid<s)return query(s,t,id<<1|1);    else return query(s,mid,id<<1)+query(mid+1,t,id<<1|1);}int main(){    int i;    while(scanf("%d",&n)){        if(n==0)break;        for(i=1;i<=n;i++){            scanf("%d",&a[i]);            pos[a[i]]=i;        }        ans=n;        ans+=min(pos[1]-1,n+1-pos[1]);        now=pos[1];    //now记录的是此时手中的球初始的位置，利用相对位置不变的性质，方便后面确定其他球的位置        build(1,n,1);        insert(pos[1],1);  //这里pos[1]已经取走        for(i=2;i<=n;i++){            int tem;            if(pos[i]>now) tem=pos[i]-now-query(now,pos[i],1);            else tem=now-pos[i]+1-query(pos[i],now,1);            ans+=min(tem,n-i+1-tem);            now=pos[i];            insert(pos[i],1);        }        printf("%I64d\n",ans);    }    return 0;}