minHeapify an array

minHeapify.ts

// stones = [2,7,4,1,8,1]
function minHeapify(arr: number[]): number[]{
    // push 0-th position to the end
    arr.push(arr[0]) // [2, 7, 4, 1, 8, 1, 2]
    // we will ignore arr[0] for math purposes
    let heap = arr
    
    let cur = Math.floor(heap.length - 1)/2 // (7-1)/2 = 6/2 = 3
    /*
             7(1)
           /    \
          4(2)   1(3)<--
         / \     /   \
      8(4) 1(5) 2(6)  
    */
    while (cur > 0) {
        let i = cur // 3
        while (2 * i < heap.length) { // left child exists
            if (2 * i + 1 < heap.length && // right  child exists
            heap[2 * i + 1] < heap[2 * i] && // right < left
            heap[i] > heap[2 * i + 1]) { // current > right
                // swap current with right child
                let tmp = heap[i]
                heap[i] = heap[2 * i + 1]
                heap[2 * i + 1] = tmp
                i = 2 * i + 1
            } else if (heap[i] > heap[2 * i]) {
                // swap left child
                let tmp = heap[i]
                heap[i] = heap[2 * i]
                heap[2 * i] = tmp
                i = 2 * i
            } else {
                break;
            }
        }
        cur = cur - 1;
    }
    return heap
}