40分蒟蒻求助

#include<bits/stdc++.h>
using namespace std;
int stone[50001],ans=0,s,n,m,head=1,ans2=0,move1=0;
bool st[50001];
void check(int l,int r,int m){
	ans=(l+r)/2;
	move1=0;
	for(int i=0;i<=n;i++){
		st[i]=0;
	}
	for(int i=0;i<=n;i++){
		head=i+1;
		if(st[i]!=0)
		    continue;
		while(st[head]!=0)
		    head++;
		while(stone[head]-stone[i]<ans){//不合法就把不合法的石头移走直到合法
			if(head==n+1){//为了防止丢掉终点的石头
				st[i]=1;
				move1++;
				break;
			}
			else{//不丢掉终点石头的正常情况
			    st[head]=1;
			    move1++;
			    head++;
			}
		}
	}
	if(move1<m)check(ans,r,m);
	if(move1>m)check(l,ans,m);
	if(move1==m){
		ans2=ans;
		return;
	}
}
int main(){
	cin>>s>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>stone[i];
	}
	if(n==0&&m==0){
		cout<<s;
		return 0;
	}//怕有毒瘤点的特判
	if(m==0){
		int x=1000000000;
		stone[n+1]=s;
		for(int i=0;i<=n;i++){
			if(stone[i+1]-stone[i]<x)
			    x=stone[i+1]-stone[i];
		}
		cout<<x;
		return 0;
	}//同上
	stone[n+1]=s;
	check(0,s,m);
	cout<<ans2;
	return 0;
}