洛谷 P3853 [TJOI2007]路标设置

路标设置

二分枚举”空旷指数“， 做法与跳石头类似。

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
//Mystery_Sky
//
#define M 10000100
#define INF 0x7f7f7f7f
#define ll long long
ll l, r, mid;
int L, n, k;
int a[M];
inline bool check(ll ans)
{
	int last = 0, cnt = 0;
	for(int i = 2; i <= n; i++) {
		while (a[i] - last > ans) {
			cnt++;
			last += ans;
		}
		last = a[i];
	}
	return cnt <= k;
}

int main() {
	scanf("%d%d%d", &L, &n, &k);
	a[0] = 0;
	for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
	a[++n] = L;
	sort(a, a+n+1);
	l = 0, r = INF;
	while(l < r) {
		mid = l + (r - l) /2;
		if(check(mid)) r = mid;
		else l = mid + 1;
	}
	printf("%lld\n", l);
	return 0;
}