RegexdrillLookahead: strip leading zeros
A regex exercise from Regexdrill. Solve it with a pattern box with live highlighting in your browser, checked against hidden test strings, and it is checked the moment you submit.
The task
Each line is a number written with digits only. Remove the zeros at the start of the line, but always leave at least one digit, so 007 becomes 7 and 000 becomes 0.
What this exercise teaches
^0+(?=\d) matches the leading zeros only as far as one digit is left after them. For 000 the engine backs off one zero to satisfy the lookahead, so a single 0 remains.
A hint if you get stuck
^0+ removes too much when the number is all zeros. Add a lookahead that demands a digit after the zeros you remove.
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