POJ2533Longest Ordered Subsequence(LIS)

Description
A numeric sequence of ai is ordered if a1 < a2 < … < aN. Let the subsequence of the given numeric sequence (a1, a2, …, aN) be any sequence (ai1, ai2, …, aiK), where 1 <= i1 < i2 < … < iK <= N. For example, sequence (1, 7, 3, 5, 9, 4, 8) has ordered subsequences, e. g., (1, 7), (3, 4, 8) and many others. All longest ordered subsequences are of length 4, e. g., (1, 3, 5, 8).

Your program, when given the numeric sequence, must find the length of its longest ordered subsequence.

Input
The first line of input file contains the length of sequence N. The second line contains the elements of sequence - N integers in the range from 0 to 10000 each, separated by spaces. 1 <= N <= 1000

Output
Output file must contain a single integer - the length of the longest ordered subsequence of the given sequence.

Sample Input

7
1 7 3 5 9 4 8

Sample Output

4

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
int num[1005],dp[1005];
int main()
{
    int n;
    while(cin>>n)
    {
    for(int i=0;i<n;i++)
    {
        cin>>num[i];
        dp[i]=1;
    }
    int ans=1;
    for(int i=1;i<n;i++)
    {
        for(int j=0;j<i;j++)
            if(num[i]>num[j])
            dp[i]=max(dp[i],dp[j]+1);
        if(dp[i]>ans)
            ans=dp[i];
    }
    cout<<ans<<endl;
    }
    return 0;
}

最简单的lis。。。却卡了我半个小时。。。例题过了却始终提交错误，最终发现将ans初始化为0导致n=1时答案错误。。。谨以此文提醒自己以后不要范类似错误。