Find Smallest Missing in Sorted

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

int main() {
#ifndef ONLINE_JUDGE
	freopen("input1.txt", "r", stdin);
	freopen("output1.txt", "w", stdout);
#endif
	int t;
	scanf("%d", &t);
	while (t--) {
		int n, m, i;
		cin >> n >> m;
		int arr[n];
		for (i = 0; i < n; i++) cin >> arr[i];
		if (arr[0] != 0)
			cout << 0 << endl;
		else if (arr[n - 1] == n - 1)
			cout << n << endl;
		else {
			int l = 0, r = n - 1, mid, ans;
			while (l <= r) {
				mid = l + ((r - l) / 2);
				if (arr[mid] == mid) {
					l = mid + 1;
				}
				else {
					if (arr[mid - 1] == mid - 1)
						ans = mid;
					r = mid - 1;
				}
			}
			cout << ans << endl;
		}
	}
	return 0;
}