【最长非升子序列】北大 POJ 1887 Testing the CATCHER

/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
    Copyright (c) 2012 panyanyany All rights reserved.

    URL   : http://poj.org/problem?id=1887
    Name  : 1887 Testing the CATCHER
    Classification : 最长非升子序列

    Date  : Wednesday, July 11, 2012
    Time Stage : half an hour

    Result:
10420937	panyanyany
1887
Accepted	224K	16MS	C++
1692B	2012-07-11 09:59:34
10420935	panyanyany
1887
Accepted	224K	16MS	C++
1692B	2012-07-11 09:59:09
10420931	panyanyany
1887
Runtime Error			C++
1691B	2012-07-11 09:58:54
10420923	panyanyany
1887
Accepted	340K	0MS	C++
1692B	2012-07-11 09:58:22

Test Data :

Review :
数组开到40005，用时0MS，减少到10005的时候，用时却是16MS……郁闷，求解释……
//----------------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <vector>

#include <algorithm>
#include <iostream>
#include <queue>
#include <set>
#include <string>

using namespace std ;

#define MEM(a, v)        memset (a, v, sizeof (a))    // a for address, v for value
#define max(x, y)        ((x) > (y) ? (x) : (y))
#define min(x, y)        ((x) < (y) ? (x) : (y))

#define INF     (0x3f3f3f3f)
#define MAXN	(1005)

#define L(x)	((x)<<1)
#define R(x)	(((x)<<1)|1)
#define M(x, y)	(((x)+(y)) >> 1)

#define DB    //

int a[MAXN], order[MAXN];

int LNotIncS(int a[], int n)
{
	int i, len, r, l, m;
	MEM(order, 0);
	len = 1;
	for (i = 0; i < n; ++i)
	{
		l = 1;
		r = len;

		while (l <= r)
		{
			m = (l + r) >> 1;
			if (order[m] >= a[i])
				l = m + 1;
			else
				r = m - 1;
		}

		if (order[l] < a[i])
			order[l] = a[i];

		if (len < l)
			len = l;
	}
	return len;
}

int main()
{
	int x, n, tc;
	n = 0;
	tc = 1;
	while (scanf("%d", &x))
	{
		if (0 == n && x == -1)
			break;

		if (x != -1)
		{
			a[n++] = x;
		}
		else
		{
			if (tc != 1)
				putchar('\n');
			printf("Test #%d:\n", tc++);
			printf("  maximum possible interceptions: %d\n", LNotIncS(a, n));
			n = 0;
		}
	}
	return 0;
}