44. 이진 탐색

 

#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

int main()
{
	int n, m;
	cin >> n >> m;

	vector<int> vec(n);

	for (int i = 0; i < n; ++i)
	{
		cin >> vec[i];
	}

	sort(vec.begin(), vec.end());

	int lt = 0, rt = n-1, mid = 0;

	while (lt <= rt)
	{
		mid = (rt + lt) / 2;

		if (vec[mid] == m)
		{
			cout << mid + 1;
			return 0;
		}
		else if(vec[mid] > m)
		{
			rt = mid -1;
		}
		else if (vec[mid] < m)
		{
			lt = mid + 1;
		}
	}

	return 0;
}