Write a Python function to find the second largest number in a list.

Question

Assisting AI · Accepted Answer

Here’s a straightforward implementation that sorts the list in descending order and returns the element at index 1. It works for lists with at least two distinct values.

```python
def second_largest(nums):
    if len(nums) < 2:
        raise ValueError("List must contain at least two elements")
    # Sort in descending order
    sorted_nums = sorted(nums, reverse=True)
    return sorted_nums[1]
```

This solution runs in O(n log n) time because of the sort. If you need an O(n) solution, you can keep track of the largest and second largest values while iterating:

```python
def second_largest(nums):
    first = second = float('-inf')
    for n in nums:
        if n > first:
            second = first
            first = n
        elif n > second and n != first:
            second = n
    if second == float('-inf'):
        raise ValueError("No second distinct largest value")
    return second
```

Both approaches correctly handle duplicates and return the second largest distinct number.

Write a Python function to find the second largest number in a list.

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