机器人

思路

• 根据嵌套得出不等式
• 化简后得出贪心策略后排序
• 因为会爆long long，用__int128替换即可

代码

// Problem: 机器人
// Contest: NowCoder
// URL: https://ac.nowcoder.com/acm/contest/9986/G
// Memory Limit: 1048576 MB
// Time Limit: 6000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp(aa,bb) make_pair(aa,bb)
#define _for(i,b) for(int i=(0);i<(b);i++)
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,b,a) for(int i=(b);i>=(a);i--)
#define mst(abc,bca) memset(abc,bca,sizeof abc)
#define X first
#define Y second
#define lowbit(a) (a&(-a))
#define debug(a) cout<<#a<<":"<<a<<"\n"
typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;
typedef long double ld;
const int N=100010;
const int INF=0x3f3f3f3f;
const int mod=1e9+7;
const double eps=1e-6;
const double PI=acos(-1.0);

struct node{
    __int128 a,b;
}t[N];

inline __int128 read()
{
    __int128 x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9')
    {
        if(ch=='-')
            f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9')
    {
        x=x*10+ch-'0';
        ch=getchar();
    }
    return x*f;
}

inline void write(__int128 x)
{
    if(x<0)
    {
        putchar('-');
        x=-x;
    }
    if(x>9)
        write(x/10);
    putchar(x%10+'0');
}

bool cmp(node x,node y){
    return x.a*y.b+x.b<y.a*x.b+y.b;
}

void solve(){
    int n;cin>>n;
    __int128 x=read(); 
    rep(i,1,n) t[i].a=read(),t[i].b=read();
    sort(t+1,t+1+n,cmp);

    rep(i,1,n){
        x=t[i].a*x+t[i].b;
    }
    write(x);
}


int main(){
    // ios::sync_with_stdio(0);cin.tie(0);
//    int t;cin>>t;while(t--)
    solve();
    return 0;
}