PKU 2828 Buy Tickets

从后往前逐个添加，每次放到第pos[i]+1个空位置上；

维护区间内空位置的个数，修改和查询都是二分查找。

# include <stdio.h>

# define ls ((r)<<1)
# define rs ((r)<<1|1)
# define mid (((x)+(y))>>1)

# define MAXN 200010

int p[MAXN], v[MAXN], a[MAXN];
int sum[4 * MAXN];

void build(int x, int y, int r)
{
    sum[r] = y-x+1;
    if (x == y) return ;
    build(x, mid, ls);
    build(mid+1, y, rs);
}

void update(int r)
{
    sum[r] = sum[ls] + sum[rs];
}

void change(int x, int y, int r, int pos)
{
    if (x == y)
    {
        sum[r] = 0;
        return ;
    }
    if (pos <= mid) change(x, mid, ls, pos);
    else change(mid+1, y, rs, pos);
    update(r);
}

void query(int x, int y, int r, int cnt, int *t)
{
    if (x == y)
    {
        *t = x;
        return ;
    }
    if (sum[ls] < cnt) query(mid+1, y, rs, cnt-sum[ls], t);
    else query(x, mid, ls, cnt, t);
}

int main()
{
    int n, i, t;
        
    while (~scanf("%d", &n))
    {
        build(1, n, 1);
        for (i = 1; i <= n; ++i) {scanf("%d%d", &p[i], &v[i]); a[i] = -1;}
        for (i = n; i >= 1; --i)
        {
            query(1, n, 1, p[i]+1, &t);
            a[t] = v[i];
            change(1, n, 1, t);
        }
        printf("%d", a[1]);
        for (i = 2; i <= n; ++i) printf(" %d", a[i]);
        putchar('\n');
    }
    
    return 0;
}