fun equationsPossible(equations: Array<String>): Boolean {
    // To adjacency list and collect not equal variables
    val adjacencyList = Array<ArrayList<Int>>(26) { ArrayList(25) }
    val notEqualVariables = ArrayList<Pair<Int, Int>>(250)
    equations.forEach { equation ->
        val firstVar = equation[0].toInt() - 97
        val isEqual = equation[1] == '='
        val secondVar = equation[3].toInt() - 97
        if (isEqual) {
            adjacencyList[firstVar].add(secondVar)
            adjacencyList[secondVar].add(firstVar)
        } else {
            notEqualVariables.add(Pair(firstVar, secondVar))
        }
    }

    val used = HashSet<Int>(equations.size)
    val variableToComponent = java.util.HashMap<Int, Int>(equations.size)
    var componentId = -1
    // For each vertex
    for (i in 0..adjacencyList.lastIndex) {
        val neighbors = adjacencyList[i]
        // For each neighbor
        for (j in 0..neighbors.lastIndex){
            val v = neighbors[j]
            if (used.contains(v)) continue
            ++componentId
            dfs(adjacencyList, v, used, variableToComponent, componentId)
        }
    }

    notEqualVariables.forEach { pair ->
        if (pair.first == pair.second) {
            return false
        }
        if (variableToComponent[pair.first] != null && variableToComponent[pair.first] == variableToComponent[pair.second]) {
            return false
        }
    }
    return true
}

fun dfs(
    adjacencyList: Array<ArrayList<Int>>,
    curVertex: Int,
    used: HashSet<Int>,
    variableToComponent: HashMap<Int, Int>,
    componentId: Int
) {
    used.add(curVertex)
    variableToComponent.put(curVertex, componentId)

    val neighbors = adjacencyList[curVertex]
    for (i in 0..neighbors.lastIndex) {
        val v = neighbors[i]
        if (used.contains(v)) continue
        dfs(adjacencyList, v, used, variableToComponent, componentId)
    }
}