Power Grid Reliability

A regional power grid consists of N districts (0 to N-1). Some districts have a power plant. Districts can be connected via high-voltage links. A district is 'powered' if it is connected to at least one district that contains a power plant. Given a list of existing links and the locations of P power plants, determine the minimum number of additional links required so that every district in the region becomes powered. Assume there is at least one power plant in the network. Example: Input: 5 2 1 0 1 2 3 4 Explanation: N=5, M=2 links, P=1 plant at district 0. Links are (1,2) and (3,4). Components are {0}, {1,2}, {3,4}. Only {0} is powered. You need 2 links to connect {1,2} and {3,4} to {0}. Output: 2