贪心 poj3045

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>

using namespace std;

class node
{
public:
    long long w,s;
    bool operator < (node n) const
    {
        return w+s<n.w+n.s;
    }
}bn[50010];

int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=0;i<n;i++)
            scanf("%I64d%I64d",&bn[i].w,&bn[i].s);
        sort(bn,bn+n);
        long long now=0;
        long long ma=-bn[0].s;
        for(int i=1;i<n;i++)
        {
            now+=bn[i-1].w;
            if(now-bn[i].s>ma)
                ma=now-bn[i].s;
        }
        cout<<ma<<endl;
    }
    return 0;
}