I am writing some code for a Binary Search Tree where each node has a left and a right child pointer. In my delete function I have the following code.
if (!current.left && !current.right) {
if (parent.left === current) {
parent.left = null;
} else {
parent.right = null;
}
} else {
if (parent.left === current) {
parent.left = current.left ? current.left : current.right;
} else {
parent.right = current.left ? current.left : current.right;
}
}
Twice I have some block with the following syntax:
if (someCondition) {
parent.left = x;
} else {
parent.right = x;
}
Is there a cleaner way to write this (maybe a one-liner)? I am not sure if there is a ternary operator syntax I can use here because I have parent.left = x in the if block and parent.right = x in the else block. I am not keen on all of these if-else blocks used in this function.
Here is the entire code snippet.
const getInOrderSuccessor = (root, node) => {
let successorParent = null;
let successor = null;
let previous = null;
let current = root;
while (current) {
if (node.value < current.value) {
successorParent = previous;
successor = current;
previous = current;
current = current.left;
} else {
previous = current;
current = current.right;
}
}
return [successor, successorParent];
};
const deleteNode = (root, value) => {
let current = root;
let parent = null;
while (current) {
if (value === current.value) break;
parent = current;
current = value < current.value ? current.left : current.right;
}
// If 2 child, deal with that first
if (current.left && current.right) {
const [successor, successorParent] = getInOrderSuccessor(root, current);
current.value = successor.value;
current = successor;
parent = successorParent;
}
if (!current.left && !current.right) {
if (parent.left === current) {
parent.left = null;
} else {
parent.right = null;
}
} else {
if (parent.left === current) {
parent.left = current.left ? current.left : current.right;
} else {
parent.right = current.left ? current.left : current.right;
}
}
};
Instead of using the parent.left = x and parent.right = x you could store the property name in a variable and use parent[direction] = x instead.
For your specific scenario it also helps that the parent.left === current check is made in both the if and else-block. This means we can move it outside the conditional.
const direction = parent.left === current ? "left" : "right";
if (!current.left && !current.right) {
parent[direction] = null;
} else {
parent[direction] = current.left ? current.left : current.right;
}
You can further simplify this by reworking your logic.
if (!a && !b) {
variable = null;
} else {
variable = a ? a : b;
}
Can be changed into:
if (a) {
variable = a;
} else if (b) {
variable = b;
} else {
variable = null;
}
Which can also be written as:
variable = a || b || null;
Resulting in the following solution:
const direction = parent.left === current ? "left" : "right";
parent[direction] = current.left || current.right || null;
Please try this one.
whenever you have something like z = y?y:x you should replace it with || operator like this z = y || x
And also you can write common conditions.
if (parent.left === current) {
parent.left = (!current.left && !current.right) ? null : (current.left || current.right);
} else {
parent.right = !(!current.left && !current.right) ? null : (current.left || current.right);
}
Here's an option that satisfies your criteria, though style-wise I like what you've written better than this :-)
function chooseWhichToMakeNull(object, condition) {
const field = condition ? 'left' : 'right';
object[field] = null;
}
const obj = { left: 5, right: 10 };
chooseWhichToMakeNull(obj, true);
console.log(obj);