Resolved: Regex for recognizing strings consisting of unique characters

^([a-z])(?!.*\1)([a-z])(?!.*\2)([a-z])(?!.*\3)([a-z])(?!.*\4)$

function createRegex(length) {<br />
    let regexString = "^";<br />
    for (let i = 1; i <= length; i++) {
        regexString += "([a-z])(?!.*\\" + i + ")"
    }
    regexString += "$";
    // Create regular expression from string
    return new RegExp(regexString, "i");
}

// Dynamically create the regular expression for a given length
let regex = createRegex(10);
// Print the regular expression
console.log(regex.source);
// Test it on a positive case
console.log(regex.test("abcdefghij")); // true
// and on a negative case
console.log(regex.test("abcDefgDij")); // false[/code]

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Or in Python:<br> 


<p>[code]import re</p>
<p>def createRegex(length):<br />
        regexString = "^"<br />
        for i in range(1, length + 1):<br />
            regexString += rf"([a-z])(?!.*\{i})"<br />
        regexString += "$"<br />
        # Create regular expression from string<br />
        return re.compile(regexString, re.I)</p>
<p># Dynamically create the regular expression for a given length<br />
regex = createRegex(10)<br />
# Print the regular expression<br />
print(regex.pattern)<br />
# Test it on a positive case<br />
print(regex.search("abcdefghij"))  # Match object<br />
# and on a negative case<br />
print(regex.search("abcDefDhij"))  # None