下面程序的运行结果为（ ）。
#include <iostream>#include <algorithm> bool check(int n, int a[], int k, int dist) { int cnt = 1; int last = a[0]; for (int i = 1; i < n; i++) { if (a[i] - last >= dist) { cnt++; last = a[i]; } } return cnt >= k;} int solve(int n, int a[], int k) { std::sort(a, a + n); int l = 0; int r = a[n - 1] - a[0]; while (l < r) { int mid = (l + r + 1) / 2; if (check(n, a, k, mid)) l = mid; else r = mid - 1; } return l;} int main() { int a[] = {1, 2, 8, 4, 9}; int n = 5; int k = 3; std::cout << solve(n, a, k) << std::endl; return 0;}