1463C - Busy Robot - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
const int N=1e6+10;
#define INF 0x3f3f3f3f3f
int a[N];
int b[N];
const int M=1010;
void solve()
{
    int n;
    cin>>n;
    for(int i=1;i<=n;++i)
        cin>>a[i]>>b[i];
    int p=0,q=0,ans=0;
    for(int i=1;i<=n;i++)
    {
        int ti;
        if(p==q)
            q=b[i];
        if(i==n||a[i+1]-a[i]>=abs(p-q))
            ti=q;
        else
            if (p < q)
                ti = p + a[i + 1] - a[i];
            else
                ti = p - a[i + 1] + a[i];
        if((b[i]-ti)*(b[i]-p)<=0)
            ans++;
        p=ti;
    }
    cout<<ans<<endl;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t;
    //t = 1;
    cin>>t;
    while (t--)
    {
        solve();
    }
}