POJ 3481 Double Queue

#include<stdio.h>
#include<string.h>
#define MAXD 1000010
int T, node, key[MAXD], client[MAXD], left[MAXD], right[MAXD], size[MAXD];
void left_rotate(int &T)
{
int k = right[T];
right[T] = left[k];
left[k] = T;
size[k] = size[T];
size[T] = size[left[T]] + size[right[T]] + 1;
T = k;
}
void right_rotate(int &T)
{
int k = left[T];
left[T] = right[k];
right[k] = T;
size[k] = size[T];
size[T] = size[left[T]] + size[right[T]] + 1;
T = k;
}
void maintain(int &T, int flag)
{
if(flag == 0)
{
if(size[left[left[T]]] > size[right[T]])
right_rotate(T);
else if(size[right[left[T]]] > size[right[T]])
left_rotate(left[T]), right_rotate(T);
else
return ;
}
else
{
if(size[right[right[T]]] > size[left[T]])
left_rotate(T);
else if(size[left[right[T]]] > size[left[T]])
right_rotate(right[T]), left_rotate(T);
else
return ;

}
maintain(left[T], 0);
maintain(right[T], 1);
maintain(T, 0);
maintain(T, 1);
}
void add(int &T, int c, int v)
{
T = ++ node;
size[T] = 1;
client[T] = c;
key[T] = v;
left[T] = right[T] = 0;
}
void Insert(int &T, int c, int v)
{
if(T == 0)
{
add(T, c, v);
return ;
}
++ size[T];
if(v < key[T])
Insert(left[T], c, v);
else
Insert(right[T], c, v);
maintain(T, v >= key[T]);
}
int Delete(int &T, int v)
{
if(v == key[T] || (v < key[T] && left[T] == 0) ||(v > key[T] && right[T] == 0))
{
int k = key[T];
if(left[T] == 0 || right[T] == 0)
T = left[T] + right[T];
else
key[T] = Delete(left[T], key[T] + 1);
return k;
}
if(v < key[T])
return Delete(left[T], v);
else
return Delete(right[T], v);
}
void select(int &T, int k, int &c, int &v)
{
int n = size[left[T]] + 1;
if(n == k)
{
c = client[T];
v = key[T];
Delete(T, v);
return ;
}
-- size[T];
if(k < n)
select(left[T], k, c, v);
else
select(right[T], k - n, c, v);
}
int main()
{
int k, c, v;
node = T = left[0] = right[0] = size[0] = 0;
for(;;)
{
scanf("%d", &k);
if(!k)
break;
if(k == 1)
{
scanf("%d%d", &c, &v);
Insert(T, c, v);
}
else if(k == 2)
{
if(size[T])
{
select(T, size[T], c, v);
printf("%d\n", c);
}
else
printf("0\n");
}
else
{
if(size[T])
{
select(T, 1, c, v);
printf("%d\n", c);
}
else
printf("0\n");
}
}
return 0;
}