BZOJ P4590[Shoi2015]自动刷题机

因为考虑到问题的单调性

直接二分最大最小值然后模拟判断一下

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
long long n,m,a[100003];
long long l,r,ans1,ans2;  
long long calc(long long x){  
    long long ans=0,sum=0;  
    for(int i=1;i<=n;i++){  
        sum=max(0ll,sum+a[i]);  
        if(sum>=x){
			sum=0; ans++;
		}
	}
    return ans;
}
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
	}
    l=1;r=99999999999999;
    while(l<r){
        long long mid=(l+r)>>1;
        if(calc(mid)<=m){
        	r=mid;
		}else{
			l=mid+1;
		}
    }
    ans1=l;
	l=1;r=99999999999999;  
    while(l<r){
        long long mid=(l+r+1)>>1;  
        if(calc(mid)>=m){
        	l=mid;
		}else{
			r=mid-1;
		}
    }
    ans2=r;
    if(calc(ans1)!=m||calc(ans2)!=m){
    	cout<<"-1"<<endl;
	}else{
		cout<<ans1<<" "<<ans2<<endl;
	}
    return 0;
}
/*

in:
4 2
2
5
-3
9

out:
3 7

*/