CC-7 : Given an integer represented as elements of array, add 1 to the integer.

Description:

Given an input integer array arr, where each index of arr represents a digit of an integer. We need to add 1 to the integer using array operations.

Test cases and expected outputs:

Input Parameters	Expected outputs
Integer 70 as array arr={7,0}	0,7,1
Integer 799 as array arr={7,9,9}	0,8,0,0
Integer 000 as array arr={0,0,0}	0,0,0,1
Integer 9999 as array arr={9,9,9,9}	1,0,0,0,0
Integer 12345 as array arr={1,2,3,4,5}	0,1,2,3,4,6

Note: 0 is added at 0th index in outputs in all rows. This is to handle cases where adding 1 may result in new index being required. Refer test case 4 above.

Pseudocode:

The java method should accept following input parameters: arr (int array). The arrays elements are the digits of the input integer to which 1 needs to be added.

Create a new array of integers addedArr with length one greater than input array arr. This new array will be used to store the arr integers elements after 1 is added to it.

Initialize a boolean variable addOneToNextIndex, which we will use as a flag to indicate that the sum of two integer digits is greater than 9, so 1 needs to be carried over to next index.

Iterate arr backwards starting from (arr.length-1) to 0 with idx as loop variable:

If idx=arr.length-1:

Add 1 to arr[idx].

If sum from above step < 10, add the sum to addedArr[idx+1].

If sum from above addition>=10, add 0 to addedArr[idx+1] and add 1 to arr[idx] in next iteration using addOneToNextIndex.

After for loop is complete, return addedArr, it contains the integer with 1 added to input integer.

Code:

public int[] arrayPlusOneToIntegerUsingArray(int[] arr) throws Exception{
	int[] addedArr=new int[arr.length+1];
	boolean addOneToNextIndex=false;
	for (int idx=arr.length-1; idx>=0; idx--) {
		if ((addOneToNextIndex==true)||(idx==arr.length-1)) {
			if (arr[idx]+1<10) {
				addedArr[idx+1]=arr[idx]+1;
				addOneToNextIndex=false;
			}else {
				addedArr[idx]=0;
				addOneToNextIndex=true;
			}
			if ((idx==0)&&(addOneToNextIndex==true)) {
				addedArr[0]=1;
			}
		}else {
			addedArr[idx+1]=arr[idx];
		}
	}
	return addedArr;	
}

Click here to download and run code and test cases !

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

public class ArrayPlusOneToIntegerUsingArray {
	
public int[] arrayPlusOneToIntegerUsingArray(int[] arr) throws Exception{
	int[] addedArr=new int[arr.length+1];
	boolean addOneToNextIndex=false;
	for (int idx=arr.length-1; idx>=0; idx--) {
		if ((addOneToNextIndex==true)||(idx==arr.length-1)) {
			if (arr[idx]+1<10) {
				addedArr[idx+1]=arr[idx]+1;
				addOneToNextIndex=false;
			}else {
				addedArr[idx]=0;
				addOneToNextIndex=true;
			}
			if ((idx==0)&&(addOneToNextIndex==true)) {
				addedArr[0]=1;
			}
		}else {
			addedArr[idx+1]=arr[idx];
		}
	}
	return addedArr;	
}
	
	
    
public static void main(String[] args) {
	ArrayPlusOneToIntegerUsingArray ap=new ArrayPlusOneToIntegerUsingArray();
	int[] addedArray;
		
	try {
	int[] intArray1 = {7,0};
	printArraySummary(intArray1, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray1);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
	int[] intArray2 = {7,9,9};
	printArraySummary(intArray2, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray2);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
	int[] intArray3 = {0,0,0};
	printArraySummary(intArray3, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray3);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
	int[] intArray4 = {9,9,9,9};
	printArraySummary(intArray4, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray4);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
	int[] intArray5 = {1,2,3,4,5};
	printArraySummary(intArray5, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray5);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
	int[] intArray6 = {9};
	printArraySummary(intArray6, "Original Array:");
	addedArray=ap.arrayPlusOneToIntegerUsingArray(intArray6);
	printArraySummary(addedArray, "Integer with 1 added is : ");
			
			
	}catch (Exception exception) {
		System.out.print("Exception: "+ exception);
	}
				
}

public static void printArraySummary(int[] intArray, String label) throws Exception {
   	// Case 1: The input Array is null !!
	if (intArray == null) { System.out.println("\n\n Input Array was null !! \n"); return; }
	// Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("************************************************************************");
	System.out.print(label+" : ");
	int arrayIndex=0;
	for (arrayIndex=0; arrayIndex< intArray.length; arrayIndex++) {
			System.out.print(intArray[arrayIndex]);
			if (arrayIndex< intArray.length-1) {System.out.print(",");}
	} 
	System.out.println();
	System.out.println("*************************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;
}

}