1. 二分左边界

2. 二分右边界

3. 砍树

#include<bits/stdc++.h>
using namespace std;
int n,m,mid;
int maxn;
int a[1000005]={};
bool check(int height)
{
	long long sum=0;
	for(int i=1;i<=n;i++)
	{
		if(a[i]<=height)
			continue;
		else
			sum+=a[i]-height;
	}
	
	return sum >= m;
}
int binary_search_right(int l,int r)
{
	while(l<r)
	{
		mid=l+r+1>>1;
		if(check(mid))
			l=mid;
		else
			r=mid-1;	
	}
	return l;	
} 
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		if(a[i]>=maxn)
			maxn=a[i];
	}
	int l=0,r=maxn;
	cout<<binary_search_right(l,r);
	return 0;
}

4. 跳石头

5.数列分段

#include<bits/stdc++.h>
using namespace std;
int n,m,mid;
int maxn;
int a[1000005]={};
bool check(int height)
{
	long long sum=0;
	for(int i=1;i<=n;i++)
	{
		if(a[i]<=height)
			continue;
		else
			sum+=a[i]-height;
	}
	
	return sum >= m;
}
int binary_search_right(int l,int r)
{
	while(l<r)
	{
		mid=l+r+1>>1;
		if(check(mid))
			l=mid;
		else
			r=mid-1;	
	}
	return l;	
} 
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		if(a[i]>=maxn)
			maxn=a[i];
	}
	int l=0,r=maxn;
	cout<<binary_search_right(l,r);
	return 0;
}

6. 补充