1 /* 2     二分：搜索距离，判断时距离小于d的石头拿掉  3 */ 4 #include 
     
       5 #include 
      
        6 #include 
       
         7 #include 
        
          8 using namespace std; 9 10 typedef long long ll;11 const int MAXN = 5e4 + 10;12 const int INF = 0x3f3f3f3f;13 ll a[MAXN];14 int n, m;15 16 bool check(ll d)    {17     int last = 0;  int cnt = 0;18     for (int i=1; i<=n+1; ++i)  {19         if (a[i] - a[last] <= d)    cnt++;20         else    last = i;21     }22     return cnt > m;23 }24 25 int main(void)  {       //POJ 3258 River Hopscotch26     //freopen ("POJ_3258.in", "r", stdin);27 28     ll x;29     while (scanf ("%I64d%d%d", &x, &n, &m) == 3)    {30         a[0] = 0;   a[n+1] = x;31         for (int i=1; i<=n; ++i)    {32             scanf ("%I64d", &a[i]);33         }34 35         sort (a, a+n+2);    ll l = 0, r = a[n+1];36         while (l <= r)   {37             ll mid = (l + r) >> 1;38             if (check (mid))    r = mid - 1;39             else    l = mid + 1;40         }41         printf ("%I64d\n", l);42     }43 44     return 0;45 }