The Alternating Trail

A mountain hiker is navigating trails between peaks. Trails are either 'Smooth' (Type 0) or 'Rough' (Type 1). The hiker's knees are weak, so they cannot traverse two 'Rough' trails consecutively. Given a map of peaks and trails, determine if there is a path from the start peak to the destination peak that obeys this rule. Input Format: - Line 1: N peaks, M trails, Start, Destination. - Next M lines: U, V, T (a trail between U and V of type T, undirected). Output Format: - 'POSSIBLE' or 'IMPOSSIBLE'. Example: Input: 4 4 0 3 0 1 1 1 2 1 2 3 0 0 2 0 Output: POSSIBLE (Explanation: 0-1-2-3 is invalid because 0-1 and 1-2 are both Rough. But 0-2-3 is Smooth-Smooth, which is valid.)