XDOJ_1095_dfs

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;

int vis[15],a[15],n,k,ans;

void dfs(int num,int v)
{
    if(num == n)
    {
        if(abs(v-a[1]) <= k)    ans++;
        return;
    }
    for(int i = 2;i <= n;i++)
    {
        if(vis[i])    continue;
        if(abs(v-a[i]) > k)    continue;
        vis[i] = 1;
        dfs(num+1,a[i]);
        vis[i] = 0;
    }
}

int main()
{
    while(~scanf("%d%d",&n,&k))
    {
        memset(vis,0,sizeof(vis));
        ans = 0;
        for(int i = 1;i <= n;i++)    scanf("%d",&a[i]);
        dfs(1,a[1]);
        printf("%d\n",ans);
    }
    return 0;
}