木材加工 --二分答案

Luogu 2440

題目分析;

• 注意$1cm$都湊不出來的情況，$r由1變爲0$，這個時候如果在進入$check$函數，$a[i]/0$就會炸

Code:

#include <bits/stdc++.h>
using namespace std;
#define maxn 100010

int n,k,a[maxn];

inline int read_() {
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9') {
		if(c=='-') f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9') {
		x=(x<<1)+(x<<3)+c-'0';
		c=getchar();
	}
	return x*f;
}
 
inline bool check_(int x) {
	int tot=0;
	for(int i=1;i<=n;++i) {
		if(tot>=k) return true;
		if(a[i]<x) continue;
		else {
			tot+=(a[i]/x);
		}
	}
	if(tot>=k) return true;
	else return false;
}

void readda_() {
	n=read_();k=read_();
	int r=0;
	for(int i=1;i<=n;++i) {
		a[i]=read_();
		r=max(r,a[i]);
	}
	int l=0,ans=0,mid;
	while(l<=r) {
		if(r==0) break;
		mid=(l+r)>>1;
		if(check_(mid)) {
			ans=mid;
			l=mid+1;
		}
		else r=mid-1;
	}
	printf("%d",ans);
}

int main() {
	freopen("a.txt","r",stdin);
    readda_();
    return 0;
}