Imagine a team of researchers exploring a remote region with limited access to power resources. They have strategically placed sensors across the area to detect potential hazards and threats to their campsite. However, these sensors consume significant power when activated. The challenge is to design an algorithm that efficiently selects the minimum number of sensors needed to establish a secure perimeter around their camp while conserving power. Propose a divide$-$and$-$conquer algorithm that, given the coordinates of n sensors placed in the region, determines the fewest number of sensors needed to be activated to create a secure perimeter around the campsite. This perimeter should encompass critical exploration areas, ensuring maximum security coverage while conserving sensor power. Explain your algorithm in detail. Give the pseudo code and analyze the time complexity $($Big$-$Oh notation$)$ of your proposed algorithm.