??????????????

??????????????????????????????????????????????????????????????????????????

????

????????????

???????????????????????????????????prev?current?next??????????

?????

function reverseList(head) {
    if (!head || !head.next) return head;
    let pre = null;
    let current = head;
    while (current) {
        let next = current.next;
        current.next = pre;
        pre = current;
        current = next;
    }
    return pre;
}

??????????????????????????next?????????next??pre???pre?????????????????????????pre????????????????????

?????

????????????????????

????????????????????pre-order?????????????????in-order????????????????post-order??????????????

???????????????????????

function kthSmallest(root, k) {
    const stack = [];
    let result = null;
    stack.push(root);
    while (stack.length > 0) {
        result = stack.pop();
        if (result.left) stack.push(result.left);
        if (result.right) stack.push(result.right);
    }
    return result;
}

????

??????????????????????????

???????????1??????1?

8 & 7 = 0 // 1000 & 0111 ? 0000

???????????1?????1?

8 | 7 = 15 // 1000 | 0111 ? 1111

?????????????1??????????

8 ^ 7 = 15 // 1000 ^ 0111 ? 1111

???????????????????????????????

function sum(a, b) {
    while (a || b) {
        const newA = a ^ b;
        const newB = (a & b) << 1;
        a = newA;
        b = newB;
    }
    return a;
}

???

??????????????????????????????????

???????

?????????????

??????????? 2*i + 1 ? 2*i + 2????? (i-1)/2?

?????

??????????

?????????

???????????????????????

?????

function heapify(array, index, size) {
    let left = index * 2 + 1;
    while (left < size) {
        let largest = left + 1 < size && array[left] < array[left + 1] ? left + 1 : left;
        if (array[index] < array[largest]) {
            swap(array, index, largest);
        } else {
            break;
        }
        index = largest;
        left = index * 2 + 1;
    }
}

??????

???????????????

??????????????????????

function maxDepth(root) {
    if (!root) return 0;
    return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
}

????

??????????

??????????????????????????????????????????

?????

function quickSort(arr, left, right) {
    if (left >= right) return arr;
    let pivot = left;
    let partitionIndex = pivot + 1;
    for (let i = partitionIndex; i < right; i++) {
        if (arr[i] < arr[pivot]) {
            swap(arr, i, partitionIndex);
            partitionIndex++;
        }
    }
    swap(arr, pivot, partitionIndex - 1);
    quickSort(arr, left, partitionIndex - 1);
    quickSort(arr, partitionIndex, right);
    return arr;
}