Find shortest distance between two islands

## Problem You are given an `R x C` binary grid where: - `1` represents land - `0` represents water The grid contains **exactly two** 4-directionally connected islands (connected via up/down/left/right). You may flip water cells (`0`) into land (`1`). Return the **minimum number of water cells to flip** so that the two islands become connected (i.e., there exists a 4-directional path of `1`s between them). ### Input - `grid`: 2D array of integers (`0` or `1`) ### Output - An integer: the minimum number of flips needed. ### Constraints (reasonable interview assumptions) - `1 <= R, C <= 200` - Exactly two islands exist. ### Example If flipping a single `0` cell can connect the islands, return `1`.