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Add 1 to number represented as array (Recursive Approach)?
In this section we will see one interesting problem. Suppose one number is given. We have to increase this number by 1. This is extremely simple task. But here we will place the number as an array. each digit of that number is placed as an element of the array. If the number is 512, then it will be stored as {5, 1, 2}. And also we have to increase the number using recursive approach. Let us see the algorithm to get the clear idea.
Algorithm
increment(arr, n, index)
Initially the default value of index is 0
begin if index < n, then if arr[index] < 9, then arr[index] := arr[index] + 1 else arr[index] := 0 increment(arr, n, index + 1) end if if index = n, then arr[n] := 1 n := n + 1 end if end
Example
#include <iostream>
#include <cmath>
#define MAX 20
using namespace std;
void increment(int num_arr[], int &n, int index = 0){
if(index < n){
if(num_arr[index] < 9){ //if digit is less than 9, add 1
num_arr[index]++;
}else{ //otherwise increase number recursively
num_arr[index] = 0;
increment(num_arr, n, index+1);
}
}
if(index == n){
num_arr[n] = 1; //add extra carry
n++; //increase n
}
}
void dispNumber(int num_arr[], int n){
for(int i = n-1; i>= 0; i--){
cout << num_arr[i];
}
cout << endl;
}
int numToArr(int num_arr[], int number){
int i = 0;
int n = log10(number) + 1;
for(int i = i; i< n; i++){
num_arr[i] = number % 10;
number /= 10;
}
return n;
}
main() {
int number = 1782698599;
int num_arr[MAX];
int n = numToArr(num_arr, number);
cout << "Initial Number: "; dispNumber(num_arr, n);
increment(num_arr, n);
cout << "Final Number: "; dispNumber(num_arr, n);
}Output
Initial Number: 1782698599 Final Number: 1782698600
Updated on: 31-Jul-2019
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