1207C - Gas Pipeline - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
	ll T;
	cin>>T;
	while(T--){
		ll n,a,b;
		scanf("%lld%lld%lld",&n,&a,&b);
		string s;
		cin>>s;
		ll ans=0;
		ll node=0,cnt=0;
		for(int i=0;i<n;i++){
			if(s[i]=='0')
				cnt++;
			else
				break;
		}
		if(cnt!=n)
			ans=(cnt+1)*a+(cnt+2)*b;
		else{
			ans=(n+1)*b+n*a;
			cout<<ans<<endl;
			continue;
		}
		
//		cout<<ans<<endl;
		
		ll cnt1=n-1;
		for(int i=n-1;i>=cnt;i--){
			if(s[i]=='0'){
				cnt1--;
			}
			else
				break;
		}
		ans+=(n-1-cnt1)*b+(n-cnt1)*a;
		
//		cout<<ans<<endl;
		
		ll sum=0;
		for(int i=cnt;i<=cnt1;i++){
			if(s[i]=='0')
				sum++;
			else{
				if(sum==1){
					ans+=a+2*b;
					ans+=a+2*b;
					sum=0;
					continue;
				}
				if(sum==0){
					ans+=a+2*b;
					sum=0;
					continue;
				}
				if((sum-1)*b>2*a){
					ans+=(sum-1)*b;
					ans+=(sum+2)*a;
					ans+=2*b;
					ans+=a+2*b;
				}
				else{
					ans+=(sum+1)*a;
					ans+=(sum+1)*2*b;
				}
				sum=0;
			}
		}
		cout<<ans<<endl;
	}
	return 0;
}