Question

How to increment an integer represented as an integer list of digits by one in Python

Answer 1

def increment_by_one(digits):
    carry = 1
    for i in range(len(digits) - 1, -1, -1):
        digits[i] += carry
        if digits[i] == 10:
            digits[i] = 0
            carry = 1
        else:
            carry = 0
            break
    
    if carry == 1:
        digits.insert(0, 1)
        
    return digits


digits = [9, 9, 9]

incremented = increment_by_one(digits)

print("Result:", " ".join(str(d) for d in incremented))

        

'''
run:

Result: 1 0 0 0

'''

 

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