1834D - Survey in Class - CodeForces Solution

#include <bits/stdc++.h>
#define BIT(x, k) ((x >> k) & 1)
#define on(x, k) (x ^ (1 << k))
using namespace std;

int n, m;
int l[100005], r[100005];

void process()
{
    cin >> n >> m;
    int l[n], r[n], shrt = m, erl = m, lat = 0;
    for (int i = 0; i < n; i++) cin >> l[i] >> r[i];
    for (int i = 0; i < n; i++)
    {
      shrt = min(shrt, r[i]-l[i]+1);
      erl = min(erl, r[i]);
      lat = max(lat, l[i]);
    }
    int res = 0;
    for (int i = 0; i < n; i++)
    {
      res = max(res, r[i]-l[i]+1-shrt);
      res = max(res, r[i]- max(l[i]-1, erl));
      res = max(res, min(r[i]+1, lat)-l[i]);
    }
    cout << (res << 1) << "\n";
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int t;
    cin >> t;
    while(t--) process();
}