POJ2828 Buy Tickets

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=2e6+14;
struct men {
    int pos;
    int val;
}Men[maxn*4];
int a[maxn];
struct node {
    int l;
    int r;
    int sum;
}segTree[maxn*4]; 
void build (int i,int l,int r) {
    segTree[i].l=l;
    segTree[i].r=r;
    segTree[i].sum=0;
    if (l==r) return;
    int mid=(segTree[i].l+segTree[i].r)>>1;
    build(i<<1,l,mid);
    build(i<<1|1,mid+1,r);
}
void add (int i,int k,int val) {
    if (segTree[i].l==segTree[i].r) {
        segTree[i].sum++;
        a[segTree[i].l]=val;
        return;
    }
    int mid=(segTree[i].l+segTree[i].r)>>1;
    int tmp=mid-segTree[i].l+1-segTree[i<<1].sum;
    if (tmp>k) add(i<<1,k,val);
    else add(i<<1|1,k-tmp,val);
    segTree[i].sum=segTree[i<<1].sum+segTree[i<<1|1].sum;
}
int main () {
    int n;
    while (~scanf("%d",&n)) {
        build(1,1,n);
        for (int i=1;i<=n;i++) {
            scanf ("%d %d",&Men[i].pos,&Men[i].val);
        }
        for (int i=n;i>=1;i--) {
            add(1,Men[i].pos,Men[i].val);
        }
        for (int i=1;i<=n;i++) {
            if (i!=1) printf (" ");
            printf ("%d",a[i]);
        }
        printf ("\n");
    }
    return 0;
}