LeetCode: Plus One

Given a non-negative number represented as an array of digits, plus one to the number.

The digits are stored such that the most significant digit is at the head of the list.

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If the lowest significant digit is not 9, we can just add one and return. Otherwise, we need to set it to 0 and make the next digit plus one.

C++ Code:

/*
 * func: plus_one
 * goal: plus one to a number stored in a digit vector
 * @param digits: vector storing digits of the number
 * return: digit vector after plus one
 */
vector<int> plus_one(vector<int> &digits){
    int iter = digits.size()-1;
    while(iter >= 0){
        digits[iter] = digits[iter] + 1;
        if(digits[iter] < 10){
            return digits;
        }else{
            digits[iter] -= 10;
            --iter;
        }
    }
    digits.insert(digits.begin(), 1);
    return digits;
}

Python Code:

# func: plus one on a number represented by a list
# @param digits: input digits list
# @return: digits list after plus one
def plus_one(digits):
    i = len(digits)-1
    while i >= 0:
        if digits[i] != 9:
            digits[i] += 1
            return digits
        else:
            digits[i] = 0
            i -= 1
    digits = [1] + digits
    return digits