Easy and simple to understand c++

#1

typedef long long int ll;

int Solution::solve(vector &a) {

ll n=a.size(),p=0,q=0;
for(int i=0;i<n;i++){
    if(i%2==0){
        p+=a[i];
    }
    else{
        q+=a[i];
    }
}
ll ans=0,x=0,y=0;
for(int i=0;i<n;i++){
    ll x1=0,y1=1;
    if(i%2==0){
        p-=a[i];
    }
    else{
        q-=a[i];
    }
    
    x1=x+q;
    y1=y+p;

    if(x1==y1){
        ans++;
    }
    
    if(i%2==0){
        x+=a[i];
    }
    else{
        y+=a[i];
    }
    
}
return ans;

}