White cattle off season May 19 H- "soil" boulder rolling (after the first addition and subtraction of greed)

Topic link: https: //ac.nowcoder.com/acm/contest/2272/H
subject to the effect:
idea: Let's count the net increase, then to increase the amount of> 0, certainly is a [i] is smaller In front of.
For the case of increasing the amount of <0. We descending order of b [i] row.

Proof: s is the minimum endurance in front of the stone.

And give an additional proof: the net increase in <0. In addition to B [n] takes a minimum value. What other sort of no effect.

#include <bits/stdc++.h>
#define LL long long
using namespace std;

struct node{
    LL a, b, c;
}a[500005];

int cmp(node &a, node &b){
    if(a.c>=0&&b.c>=0){
        return a.a<b.a;
    }
    else if(a.c<0&&b.c<0){
        return a.b>b.b;
    }
    else{
        return a.c>b.c;
    }
}

int main()
{
    int t;
    scanf("%d", &t);
    while(t--){
        LL n, m;
        scanf("%lld%lld", &n, &m);
        for(int i=1; i<=n; i++){
            scanf("%lld%lld", &a[i].a, &a[i].b);
            a[i].c=a[i].b-a[i].a;
        }
        sort(a+1, a+1+n, cmp);
        for(int i=1; i<=n; i++){

            m-=a[i].a;
            if(m<0){
                break;
            }
            else{
                m+=a[i].b;
            }
        }
        if(m>=0){
            printf("Yes\n");
        }
        else{
            printf("No\n");
        }
    }

    return 0;
}