[백준 2512] 예산 (Binary Search) (C/C++) (★)

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <string.h>
#include <math.h>
#include <vector>
using namespace std;
 
long long N;
long long total;
long long budget[10010];
 
long long cal(long long mid)
{
    long long sum = 0;
    
    for(int i = 1; i <= N; i++)
    {
        if(budget[i] <= mid)
        {
            sum += budget[i];
        }
        else
        {
            sum += mid;
        }
    }
        
    return sum;
}
 
int main(void)
{
//    freopen("B2512_input.txt", "r", stdin);
 
    cin >> N;
    
    for(int i = 1; i <= N; i++)
    {
        cin >> budget[i];
    }
    sort(budget+1, budget+N+1);
    
    cin >> total;
    
    long long left = 1;
    long long right = budget[N];
    long long Max = 0; 
    
    while(left <= right)
    {
        // 상한액 
        long long mid = (left + right) / 2;
        
        // 예산
        long long sum = cal(mid); 
 
        if(sum > total)
        {
            right = mid-1;
        }
        else if(sum <= total)
        {
            if(Max < mid)
            {
                Max = mid;
            }
            
            left = mid+1;
        }
    }
    
    cout << Max;
 
    return 0;
}