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# Hacker Rank: Day 9: Recursion 3

Recursive Method for Calculating Factorial

factorial(N) = {1/n X  factorial(N-1) N ≤ 1/otherwise

Function Description

Complete the factorial function in the editor below.

Be sure to use recursion.

factorial has the following paramter:

• int n: an integer

Returns

• int: the factorial of n

Note: If you fail to use recursion or fail to name your recursive function factorial or Factorial, you will get a score of 0

Input Format

A single integer n,(the argument to pass to factorial).

Constraints

2 ≤ n ≤ 12

Sample Input

3

Sample Output

6

Explanation

Consider the following steps. After the recursive calls from step 1 to 3, results are accumulated from step 3 to 1.

1.factorial(3) = 3 x factorial(2) = 3 x 2 = 6

2.factorial(2) = 2 x factorial(1) = 2 x 1 = 2

3.factorial(1) = 1

PHP Solutions:

`// Complete the factorial function below.function factorial(\$n) {    if (\$n == 0) {        return 1;    } else {        return \$n * factorial(\$n - 1);    }}`
`\$fptr = fopen(getenv("OUTPUT_PATH"), "w");\$stdin = fopen("php://stdin", "r");fscanf(\$stdin, "%d\n", \$n);\$result = factorial(\$n);fwrite(\$fptr, \$result . "\n");fclose(\$stdin);fclose(\$fptr); `

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