贪心 ：按重量值和强壮值从小到大排序即为最优解

牛 交换前 交换后
i −s(i) w(i+1)−s(i)
i+1 w(i)−s(i+1) −s(i+1)

比较即可

AC代码

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

#define N 50001

typedef pair < int , int > PII;

int n;
PII Q[N];

int main()
{
    cin >> n;

    for (int i = 1; i <= n; i++)
    {
        int w , s;
        cin >> w >> s;
        Q[i] = { w + s , w };
    }

    sort(Q + 1,Q + 1 + n);

    int ans = -0x3f3f3f3f,sum = 0;

    for (int i = 1; i <= n; i++)
    {
        int s = Q[i].first - Q[i].second;
         ans = max(ans , sum - s);
         sum += Q[i].second;
    }

    cout << ans;
    return 0;
}