POJ 3093 Stock Exchange - (DP)

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题目链接：http://poj.org/problem?id=3903

#include <stdio.h>  
#include <vector>   
#include <algorithm>
using namespace std;

//POJ 3903 Stock Exchange

int main()
{
    int N;
    while (scanf("%d", &N) != EOF)
    {
        vector<int> v(N), dp(N, 1), h(N, -1); // h(i)=j, j is the max which dp[j]>dp[i], otherwise -1.
        int _max = 0;
        for (int i = 0; i < N; i++)
        {
            scanf("%d", &v[i]);
            for (int j = i - 1; j >= 0;)
            {
                if (dp[j] >= dp[i])
                {
                    if (v[j] < v[i])
                    {
                        dp[i] = dp[j] + 1;
                        j = h[j]; // dp[k] < dp[i] is meaningless
                    }
                    else j--;
                }
                else j = h[j];
            }
            // maintain h[i]
            for (int k = i - 1; k >= 0;)
            {
                if (dp[k] > dp[i])
                {
                    h[i] = k;
                    break;
                }
                else k = h[k];
            }
            _max = max(_max, dp[i]);
        }
        printf("%d\n", _max);
    }
    system("pause");
    return 0;
}