首发题解！

洛谷传送门

#include <bits/stdc++.h>
using namespace std;
struct node{
    int x,id;
}a[50010];
map<int,int> m;
map<int,int> m1;
bool cmp(node x,node y){
    return x.x < y.x;
}
int main(){
    int n,pz = 0,minn = INT_MAX;
    cin >> n;
    for(int i = 1;i <= n;i++){
        cin >> a[i].x >> a[i].id;
        m[a[i].id]++;
    }
    sort(a + 1,a + 1 + n,cmp);
    int l = 1,r = 1;
    for(;r <= n;r++){
        m1[a[r].id]++;
        if(m1[a[r].id] == 1) pz++;
        while(pz == m.size()){
            minn = min(minn,(a[r].x - a[l].x));
            m1[a[l].id]--;
            if(m1[a[l].id] == 0) pz--;
            l++;
        }
    }    
    cout << minn;
    return 0;
}