堆 Heap

手写堆

int size = 0;//堆的大小
int heap[maxn];
void push( int x )
{
    int i = size;
    while( i > 0 )
    {
        int p = (i - 1)/2;
        if( heap[p] <=x )
            break;

        heap[i] = heap[p];
        i = p;
    }
    heap[i] = x;
    size ++;
}

int pop( )
{
    int ret = heap[0];
    int x = heap[--size];
    int i = 0;
    while( (2*i + 1) < size )
    {
        int a = 2*i + 1;
        int b = 2*i + 2;
        if( b<size && heap[b] < heap[a] )
            a = b;
        if(heap[a] > x)
            break;
        heap[i] = heap[a];
        i = a;
    }
    heap[i] = x;
    return ret;
}