LeetCode-193: Valid Phone Numbers

193. Valid Phone Numbers

Solution

grep -E '^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$|^[0-9]{3}-[0-9]{3}-[0-9]{4}$' file.txt

Valid Phone Numbers Explanation

Correct Regular Expressions

Pattern for (xxx) xxx-xxxx:

^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$

Pattern for xxx-xxx-xxxx:

^[0-9]{3}-[0-9]{3}-[0-9]{4}$

Example Workflow

Given the input file file.txt containing:

987-123-4567
123 456 7890
(123) 456-7890
text 123-456-7890
(123) 456-7890 text

The command processes it as follows:

grep -E '^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$|^[0-9]{3}-[0-9]{3}-[0-9]{4}$' file.txt

Expected Output

987-123-4567
(123) 456-7890

Debugging and Attempts

Original Attempt

grep -E '^\(\d{3}\) \d{3}-\d{4}$|^\d{3}-\d{3}-\d{4}$' file.txt

Failed due to incorrect digit matching.

Corrected Solution

grep -E '^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$|^[0-9]{3}-[0-9]{3}-[0-9]{4}$' file.txt

Uses [0-9] instead of \d for better compatibility.

Debugging Script

To verify line-by-line matching:

while IFS= read -r line; do
    echo "Checking: '$line'"
    if echo "$line" | grep -E '^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$|^[0-9]{3}-[0-9]{3}-[0-9]{4}$'; then
        echo "Matched: $line"
    else
        echo "Not Matched: $line"
    fi
done < file.txt

Final Thoughts

This solution ensures correct pattern matching for valid phone numbers in the specified formats, using extended regex for better readability and compatibility.