题解 | 知识竞赛

#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

int n;

int main()
{
     cin >> n;
     vector<vector<int>> a(n, vector<int>(2));
     for(int i = 0; i < n; i++)
     {
        cin >> a[i][0] >> a[i][1];
     }
     sort(a.begin(), a.end(), [](auto& a1, auto& a2) { return abs(a1[0] - a1[1]) < abs(a2[0] - a2[1]); });
    
    int maxa = a[0][0], maxb = a[0][1];
    int ans = 0;
    for(int i = 1; i < n; i++)
    {
        if(a[i][0] <= a[i][1]) ans = max(ans, maxa + a[i][0]);
        else ans = max(ans, maxb + a[i][1]);
        maxa = max(maxa, a[i][0]);
        maxb = max(maxb, a[i][1]);
    }

    cout << setprecision(1) << fixed << (double) ans / 2;

    return 0;
}