题目传送门
1 /*
2 二分：搜索距离，判断时距离小于d的石头拿掉
3 */
4 #include <cstdio>
5 #include <algorithm>
6 #include <cstring>
7 #include <cmath>
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 Hopscotch
26 //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
", l);
42 }
43
44 return 0;
45 }