또~~~~ 버 플로우(경우를 세는 경우 오버플로우 날 수 있다)

3079번: 입국심사

틀림(22번째 줄에서 오버플로우 남)

#include <bits/stdc++.h>
#define endl '\n' // don't use when you cover interactive problem
#define all(v) v.begin(), v.end()
 
using namespace std;
typedef long long ll;
 
int main() {
    ios::sync_with_stdio(false), cin.tie(0);
 
    ll N, M; cin >> N >> M;
    vector<ll> v(N);
    for(auto& i: v) cin >> i;
 
    ll lo = 1, hi = 1e18;
    ll ans = -1;
    while(lo <= hi){
        ll mid = (lo+hi)/2;
        ll cnt = 0;
        bool flag = false;
        for(auto& i: v){
            cnt += mid/i;
        }
        if(cnt >= M){
            ans = mid;
            hi = mid - 1;
        }
        else lo = mid + 1;
    }    
    cout << ans << endl;
 
    return 0;
}cs

데이터 출처 https://www.acmicpc.net/board/view/88014

input.txt

0.29MB

다음과 같이 수정해야 맞는다

#include <bits/stdc++.h>
#define endl '\n' // don't use when you cover interactive problem
#define all(v) v.begin(), v.end()
 
using namespace std;
typedef long long ll;
 
int main() {
    ios::sync_with_stdio(false), cin.tie(0);
 
    ll N, M; cin >> N >> M;
    vector<ll> v(N);
    for(auto& i: v) cin >> i;
 
    ll lo = 1, hi = 1e18;
    ll ans = -1;
    while(lo <= hi){
        ll mid = (lo+hi)/2;
        ll cnt = 0;
        bool flag = false;
        for(auto& i: v){
            cnt += mid/i;
            if(cnt >= M){
                flag = true;
                break;
            }
        }
        if(cnt >= M){
            ans = mid;
            hi = mid - 1;
        }
        else lo = mid + 1;
    }    
    cout << ans << endl;
 
    return 0;
}cs