Rust: What is the difference between push and extend?

push — add one element. extend — add multiple elements.

push:

• Single element.
• O(1) amortized.
• One at a time.

extend:

• Multiple elements.
• Iterator.
• Batch operation.

1let mut v = vec![1, 2, 3];
2v.push(4);  // v: [1, 2, 3, 4]
3
4let mut v = vec![1, 2, 3];
5v.extend([4, 5, 6]);  // v: [1, 2, 3, 4, 5, 6]

Key: push for single, extend for multiple.