POJ 1887 —— Testing the CATCHER 最长下降子序列

原题：http://poj.org/problem?id=1887

求最长下降子序列个数

注意输出格式！

O（n²）

#include<cstdio>
#include<algorithm>

using namespace std;
int dp[100000000];
int a[100000000];
int cas = 0;
int main()
{
	int tmp;
	while(~scanf("%d", &tmp))
	{
		if(tmp == -1)	break;
		int cnt = 0;
		a[cnt++] = tmp;
		while(1)
		{
			scanf("%d", &tmp);
			if(tmp == -1)	break;
			a[cnt++] = tmp;
		}
		for(int i = 0;i<cnt;i++)
			dp[i] = 1;
		int ans = 1;
		for(int i = 1;i<cnt;i++)
		{
			for(int j = 0;j<i;j++)
			{
				if(a[i] < a[j] && dp[i] < dp[j] + 1)
				dp[i] = dp[j] + 1;
			}
			ans = max(ans, dp[i]);
		}
		printf("Test #%d:\n", ++cas);
		printf("  maximum possible interceptions: %d\n\n", ans);
	}
	return 0;
}

O（nlogn）

#include<cstdio>
#define inf 99999999
int stack[100000000];
int cas = 0;

int main()
{
	int tmp;
	while(~scanf("%d", &tmp))
	{
		if(tmp == -1)	break;
		int top = 1;
		stack[1] = tmp;
		while(1)
		{
			scanf("%d", &tmp);
			if(tmp == -1)	break;
			if(tmp < stack[top])
			stack[++top] = tmp;
			else
			{
				int l = 1, r = top;
				int mid;
				while(l <= r)
				{
					mid = (l + r) / 2;
					if(tmp > stack[mid])
						r = mid - 1;
					else
						l = mid + 1;
				}
				stack[l] = tmp;
			}	
		}		
		printf("Test #%d:\n", ++cas);
		printf("  maximum possible interceptions: %d\n\n",top);
	}
	return 0;
}