class SegTree(val array: IntArray){
    private var treeArray:MutableList<Int>
    private var arrSize: Int
    
    init{
        treeArray = MutableList<Int>(4*array.size){0}
        initSegTree(array,0,0,array.size-1)
        arrSize = array.size
        println(treeArray)
    }

    private fun initSegTree(array: IntArray, treeIndex:Int, start:Int, end:Int) : Int {
        if(start == end){
            treeArray[treeIndex] = array[start]
        }else{
            val mid:Int = start + (end - start)/2
            treeArray[treeIndex] = initSegTree(array,2*treeIndex+1,start,mid) + initSegTree(array,2*treeIndex+2,mid+1,end)
        }

        return treeArray[treeIndex]
    }

    private fun queryHelper(treeIndex:Int, currStart:Int, currEnd:Int, start:Int, end:Int) : Int{
        return if(currStart > end || currEnd < start){
            return 0
        }else if(currStart == currEnd){
            treeArray[treeIndex]
        }else if(currStart >= start && currEnd <= end){
            treeArray[treeIndex]
        }else{
            val mid = currStart+ (currEnd - currStart)/2
            queryHelper(2*treeIndex+1,currStart,mid,start,end) + queryHelper(2*treeIndex+2,mid+1,currEnd,start,end)
        }
    }

    private fun updateHelper(treeIndex:Int, currStart:Int, currEnd:Int, start:Int, end:Int, value: Int) : Int{
        if(currStart>end || currEnd < start){
            return treeArray[treeIndex]
        }

        if(currStart == currEnd){
            treeArray[treeIndex]+=value
        }else{
            val mid:Int = currStart + (currEnd - currStart)/2
            treeArray[treeIndex] = updateHelper(2*treeIndex+1,currStart,mid,start,end,value) + 
                updateHelper(2*treeIndex+2,mid+1,currEnd,start,end,value) 
        }

        return treeArray[treeIndex]
    }

    fun queryInterval(start: Int, end: Int) : Int {
        return queryHelper(0,0,arrSize-1,start,end)
    }

    fun updateInterval(start: Int, end: Int, value : Int){
        updateHelper(0,0,arrSize-1,start,end,value)
    }

    fun printSegTree(){
        println(treeArray)
    }
    
}

fun main(args: Array<String>) {
    val input = intArrayOf(1,2,3,1,3,5,6,4,1,2)
    val segTree = SegTree(input)
    println(segTree.queryInterval(3,7))
    segTree.updateInterval(0,3,2)
    segTree.printSegTree()
}