uva 10154

dp  记忆化搜索 做的时候像dfs 

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>

using namespace std;

struct tur
{
    int x,y,s;
} tur[6000];
int d[6000] = {},n;
int flag[6000] = {};
int _max;
int dp(int i)
{
    int& ans = d[i];
    if(d[i])
        return ans;
    ans = 1;
    for(int j = 1; j < n; j++)
    {
        if(tur[j].x < tur[i].s && !flag[j])
        {
            flag[j] = 1;
            ans = max(ans, dp(j)+1);
            flag[j] = 0;
        }
    }
    return ans;
}
int main()
{
    n = 1;
    tur[0].s = 0x7fffffff;
    while(scanf("%d%d",&tur[n].x,&tur[n].y) == 2)
    {
        tur[n].s = tur[n].y-tur[n].x;
        n++;
    }
    _max = 0;
    for(int i = 1; i < n; i++)
    {
        //memset(d, 0, sizeof(d));
        flag[i] = 1;
        _max = max(_max, dp(i));
        flag[i] = 0;
    }
    printf("%d\n",_max);
    return 0;
}