The ultimate guide to coding interviews. Developed by FAANG engineers. Boost problem-solving skills with number theory, dynamic programming, and graph theory. Get interview-ready in just a few hours.

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Whether you’re gearing up for online coding challenges, code-a-thons, or interviews, then this course is for you. With this course, you will solidify your problem-solving skills ensuring a swift sail through any problem. 


You will be tasked with solving some of the most frequently asked questions that are brought up in FAANG interviews. You will start with the concepts of Number Theory and Divide and Conquer, and gradually move towards more complex problems like dynamic programming and graph theory.


With each problem you solve, there will be insightful explanations and full implementation details to really hammer home the concepts. By the time you finish this course, you will have the confidence to solve any problem, no matter the difficulty.

Competitive Programming - Crack Your Coding Interview, C++

# Problem statement
***Given a number `n`, convert each digit of that number to its corresponding string. Make sure the order is correct.**

For example, let us take **n = 278**. The output should be **two seven eight**.

# Solution: **Recursive approach**

The problem looks very easy and it could have been implemented without using Recursion. But to understand the concept of Recursion, it is very important that we discuss some basic problems too.

Let us first visualize how Recursion might help in solving this problem.

#include <iostream>
using namespace std;

char spellings[][10]={"zero","one","two","three","four","five","six","seven","eight","nine"};

void print(int n){
    if(n==0){
        return;
    }
    print(n/10);
    cout<< n << spellings[n%10]<<" ";

}

int main() {
    print(234);
}


**Explanation:**

* On line 4, we define an array `spellings`, which will store the string representation of each number. (*${i^{th}}$ digit  has its corresponding string stored at ${i^{th}}$  index of the array*).
* On line 6, we define our function `print()`, which will accept the number `n` and will print the result.
* On line 7, we check if we reach the base case. If so, then we return.
* On line 10, we call the function recursively by passing the value of `n` as ${\frac{n}{10}}$ (We need to extract single digits from the number).
* On line 11, we print the string corresponding to that digit.
* In the `main()` function, we call our function by passing a number.

Learn to use Recursion to solve coding problems.

Overview

Number Theory

Number Theory

Divide and Conquer

Greedy Algorithms

Greedy Algorithms

Recursion and Backtracking

Recursion and Backtracking

Dynamic Programming

Graphs

Bonus Lessons

Convert Digits to Strings

Problem statement