UVA 1442(p249)----Cave

#include<iostream>
#include<cstdio>
using namespace std;
const int maxn=1000000+50;
int p[maxn],s[maxn],water[maxn];
int t,n;
int main()
{
ios::sync_with_stdio(false);
cin>>t;
while(t--)
{
cin>>n;
int ans=0,h;
for(int i=0;i<n;i++) cin>>p[i];
for(int i=0;i<n;i++) cin>>s[i];
h=s[0];
for(int i=0;i<n;i++)
{
if(h<p[i]) h=p[i];
if(h>s[i]) h=s[i];
water[i]=h;
}
h=s[n-1];
for(int i=n-1;i>=0;i--)
{
if(h<p[i]) h=p[i];
if(h>s[i]) h=s[i];
ans+=min(water[i],h)-p[i];
}
cout<<ans<<endl;
}
return 0;
}