poj1065 Wooden Sticks

思路：

贪心，最长下降子序列 二分。

实现：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <windows.h>
const int INF = 0x3f3f3f3f;
using namespace std;
struct node
{
    int x, y;
};
node a[5005];
int d[5005];
bool cmp(const node & a, const node & b)
{
    if (a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}
void work(int x, int end)
{
    int l = 1, r = end, m, res = INF;
    while (l <= r)
    {
        m = (l + r) >> 1;
        if (d[m] <= x)
        {
            r = m - 1;
        }
        else
        {
            res = m;
            l = m + 1;
        }
    }
    if (res != INF)
        d[res + 1] = x;
    else
        d[1] = x;
}
int main()
{
    int t, n;
    cin >> t;
    while (t--)
    {
        cin >> n;
        for (int j = 0; j < n; j++)
            scanf("%d %d", &a[j].x, &a[j].y);
        sort(a, a + n, cmp);
        int ans = 1;
        d[1] = a[0].y;
        for (int i = 1; i < n; i++)
        {
            if (a[i].y < d[ans])
                d[++ans] = a[i].y;
            else
                work(a[i].y, ans-1);    
        }
        cout << ans << endl;    
    }
    return 0;
}