Plus One

 Given a non-empty array of digits representing a non-negative integer, increment one to the integer.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contains a single digit.

You may assume the integer does not contain any leading zero, except the number 0 itself.

 

Example 1:

Input: digits = [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

Input: digits = [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

Example 3:

Input: digits = [0]
Output: [1]

 

Constraints:

• 1 <= digits.length <= 100
• 0 <= digits[i] <= 9

Solution:

Algorithm:

1) Add 1 to the nth element in the array. If the sum is greater than 9 then take the ten's element (save it to 'carry') and move to the (n-1)th element. 

2) Continue step 1 till we don't have a carry.

	public class Solution {
	public int[] PlusOne(int[] digits) {
	int len = digits.Length;
	if(len == 0){
	return digits;
	}
	int i=len-1;
	int carry = 1;
	while(i>=0){
	if(digits[i]+carry>9){
	int pcarry = (digits[i]+carry)/10;
	digits[i] = (digits[i]+carry)%10;
	carry = pcarry;
	}
	else{
	digits[i] = digits[i]+carry;
	carry = 0;
	}
	if(carry == 0){
	break;
	}
	i--;
	}
	if(carry>0){
	int[] tDigits = new int[len+1];
	tDigits[0] = carry;
	for(i=0;i<len;i++){
	tDigits[i+1] = digits[i];
	}
	digits = tDigits;
	}
	return digits;
	}
	}

view raw PlusOne.cs hosted with ❤ by GitHub

Time Complexity:  O(n)

Space Complexity: O(1)