Biggest Single Number — LeetCode 619 Python Solution

The problem

A single number is a value that appears exactly once in the table. Report the largest single number, or null when every value appears more than once. The MyNumbers table has one row per value and may contain duplicates: num (int).

Example

MyNumbers table:

| num |
| --- |
| 12  |
| 7   |
| 12  |
| 30  |
| 4   |

Result:

| num |
| --- |
| 30  |

The values 7, 30 and 4 each appear once while 12 appears twice, so the largest single number is 30; had every value been repeated the answer would be null.

Python solution

import pandas as pd

def biggest_single_number(my_numbers: pd.DataFrame) -> pd.DataFrame:
    counts = my_numbers['num'].value_counts()
    singles = counts[counts == 1]
    if singles.empty:
        return pd.DataFrame({'num': [None]})
    return pd.DataFrame({'num': [int(singles.index.max())]})

Complexity

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