HDU 2037 - 今年暑假不AC（贪心 + 动态）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2037

贪心算法：

#include<iostream>
#include<algorithm>
using namespace std;
struct TV{
	int begin;
	int end;
}Tv[105];
bool cmp(TV a,TV b)
{
	return a.end < b.end;
} 
int main()
{
	int n, i;
	while(cin >> n && n != 0)
	{
		int count = 1;
		for(i = 0; i < n; i++)
		{
			cin >> Tv[i].begin >> Tv[i].end;
		}
		sort(Tv,Tv+n,cmp);
	
		int End=Tv[0].end;
		for(i=1; i<n; i++)
		{
			if(Tv[i].begin >= End)
			{
				count++;
			    End = Tv[i].end;
			}
		}
		cout << count << endl;
	}
	return 0;
}

动态规划：

#include <stdio.h>
#include <stdlib.h>

struct c
{
    int x;
    int y;
    int ord;
}d[100];

int cmp(const struct c *a, const struct c *b)
{
    if ((*a).x == (*b).x)
        return (*a).y - (*b).y;
    else
        return (*a).x - (*b).x;
}

int main(void)
{
    int i, j, n, max;

    while (scanf("%d", &n), n)
    {
        for (max = i = 0; i < n; i++)
        {
            scanf("%d%d", &d[i].x, &d[i].y);
            d[i].ord = 1;
        }
        qsort(d, n, sizeof(struct c), cmp);
        d[n-1].ord = 1;
        for (i = n - 2; i >= 0; i--)
        {
            for (j = i + 1; j < n; j++)
            {
                if (d[i].y <= d[j].x && d[i].ord < d[j].ord + 1)
                    d[i].ord = d[j].ord + 1;
            }
            if (max < d[i].ord)
                max = d[i].ord;
        }
        printf("%d\n", max);
    }

    return 0;
}