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

Plus One.cpp

class Solution {
public:
    vector<int> plusOne(vector<int> &digits) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        for(int i = 0; i < digits.size() / 2; ++i) {
            swap(digits[i], digits[digits.size() - i - 1]);
        }
        
        
        int remainder = 1;
        int index = 0;
        while(remainder != 0) {
            if(digits.size() == index) {
                digits.push_back(0);
            }
            
            digits[index] += remainder;
            if(digits[index] == 10) {
                digits[index] = 0;
                remainder = 1;
            } else {
                remainder = 0;
            }
            ++index;
        }
        
        for(int i = 0; i < digits.size() / 2; ++i) {
            swap(digits[i], digits[digits.size() - i - 1]);
        }
        
        
        return digits;
    }
};