66. Plus One (Easy)

Solution

• Start from the end of the vector.
• maintain a carry every time you add a digit.
• finally if carry greater than 0 then add it to the star of vector.
• TC: O(N)
• SC: O(1)

Code

class Solution {
public:
    vector<int> plusOne(vector<int>& digits) {
        int n = digits.size();
        int carry = 1;
        for(int i = n-1;i>=0;i--){
            digits[i]+=carry;
            if(digits[i]>9){
                carry = digits[i]/10;
                digits[i]%=10;
            }else{
                carry = 0;
            }
        }
        if(carry>0) digits.insert(digits.begin(),carry);
        return digits;
    }
};