POJ2533Longest Ordered Subsequence（DP）

http://poj.org/problem?id=2533

在经典不过的DP题目了。。。。

#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cmath>
#include <ctime>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
#define INF 0x3f3f3f3f
#define MAX(a,b) (a > b ? a : b)
#define MIN(a,b) (a < b ? a : b)
#define mem0(a) memset(a,0,sizeof(a))

typedef long long LL;
const double eps = 1e-12;
const int MAXN = 1005;
const int MAXM = 5005;

int DP[1100], a[1100], N;

int BinarySearch(int low, int high, int val)
{
    while(low < high)
    {
        int mid = (low + high) >> 1;
        if(DP[mid] < val) low = mid +1;
        else high = mid;
    }
    return low;
}

int main()
{
    while(~scanf("%d", &N))
    {
        for(int i=1;i<=N;i++)
        {
            scanf("%d", &a[i]);
        }
        DP[1] = a[1];
        int len = 1;
        for(int i=2;i<=N;i++)
        {
            int id = BinarySearch(1, len+1, a[i]);
            DP[id] = a[i];
            if(id > len) ++len;
        }
        printf("%d
", len);
    }
    return 0;
}