Regex替换需求：在字符串首个0前添加连字符

Alright, let's tackle this regex replacement problem. The goal is to add a hyphen immediately before the first occurrence of '0' in your 11-character input string, producing a 12-character output where no letters appear after the hyphen. Here's how to do it:

Regex Pattern & Replacement #

The core approach uses a non-greedy capture to isolate the part before the first '0', then inserts the hyphen between that part and the '0'.

• Match Pattern: ^(.*?)(0)
• Replacement String: $1-$2 (use \1-\2 in some regex engines like Python's re module)

Breakdown of the Regex #

• ^: Anchors the match to the start of the string, ensuring we don't accidentally match '0's in unrelated positions later in the string.
• (.*?): Non-greedy capture group that grabs all characters from the start up to (but not including) the first '0'. The ? makes the wildcard non-greedy, so it stops at the very first '0' instead of the last one.
• (0): Captures the first '0' itself, so we can include it in the output right after the hyphen.

Code Examples #

Here's how to implement this in common programming languages:

Python #

import re

def format_target_string(s):
    # Optional validation to ensure input meets the 11-character requirement
    if len(s) != 11:
        raise ValueError("Input must be exactly 11 characters long")
    return re.sub(r'^(.*?)(0)', r'\1-\2', s)

# Test the provided examples
print(format_target_string("RC000030034"))  # Output: RC-000030034
print(format_target_string("RC100003282"))  # Output: RC1-00003282

JavaScript #

function formatTargetString(str) {
    if (str.length !== 11) {
        throw new Error("Input must be exactly 11 characters long");
    }
    return str.replace(/^(.*?)(0)/, '$1-$2');
}

// Test cases
console.log(formatTargetString("RC000030034")); // "RC-000030034"
console.log(formatTargetString("RC100003282")); // "RC1-00003282"

Verification #

• For input RC000030034, the regex captures RC as the first group and 0 as the second. Replacing gives RC-0 followed by the remaining digits, resulting in the correct 12-character output.
• For input RC100003282, the first group captures RC1, the second captures 0, leading to RC1-0 plus the rest of the digits.

This solution adheres to all your requirements: fixed input/output lengths, hyphen only before the first '0', and no letters after the hyphen.

内容的提问来源于stack exchange，提问作者TimmyT