1608. Special Array With X Elements Greater Than or Equal X

class Solution {
public:
    int specialArray(vector<int>& nums) {
        int i = 1, j = *max_element(nums.begin(), nums.end()); //5
        while (i <= j) {
            int mid = i + (j - i) / 2;
            int count = 0;
            for (int k = 0; k < nums.size(); k++) {
                if (nums[k] >= mid) {
                    count++;
                }
            }
            if (count == mid) {
                return mid;
            } else if (count < mid) {
                j = mid - 1;
            } else {
                i = mid + 1;
            }
        }
        return -1;
    }
};