Day 15 - Recursion Series Part C

Today’s Problem - Pascal’s Triangle

Question – Write a function that takes an integer n as input and prints first n lines of Pascal’s Triangle

Example

input: 5 output: 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 

JavaScript Implementation

Solution

/** * @author MadhavBahl * @date 09/01/2018 */ function findPascal (row, col) { if (col === 1 || col === row) { return 1; } else { return findPascal (row-1, col-1) + findPascal (row-1, col); } } function printPascal (num) { let currentRow; for (let i=1; i<=num; i++) { currentRow = ''; for (let j=1; j<=i; j++) { currentRow += findPascal (i, j) + ' '; } console.log(currentRow); } } console.log ('/* ===== Pascal\'s Triangle for n = 5\n'); printPascal (5); console.log ('\n/* ===== Pascal\'s Triangle for n = 7\n'); printPascal (7); 

C++ Implementation

Solution

/** * @author:divyakhetan * @date: 10/1/2019 */ #include<bits/stdc++.h> using namespace std; int sum(int n){ if(n < 10) return n; else return n % 10 + sum(n /10); } int main(){ int n; cin >> n; cout << "The sum of digits is " << sum(n); return 0; } 

C++ Solution by @profgrammer

/* *@author: profgrammer *@date: 09-01-2019 */ #include <bits/stdc++.h> using namespace std; int ncr(int n, int r){ if(n < r || n < 0 || r < 0) return 0; if(n == r || r == 0) return 1; return ncr(n-1,r) + ncr(n-1, r-1); } int main() { int n; cin>>n; for(int i = 0;i <= n;i++){ for(int j = 0;j <= i;j++) cout<<ncr(i,j)<<" "; cout<<endl; } } 

Python Implementation

[Solution] (./Python/pascal.py)

=begin @author:aaditkamat @date: 9/1/2019 =end def fill_table(num) table = [] (num).times do table.push([].fill(0, 0, num)) end num.times do |i| table[i][0] = 1 end i = 1 until i >= num do j = 1 until j >= num do table[i][j] = table[i - 1][j] + table[i - 1][j - 1] j += 1 end i += 1 end table end def print_table(table) i = 0 until i >= table.length do j = 0 until j >= table.length do if table[i][j] != 0 print "#{table[i][j]} " end j += 1 end print "\n" i += 1 end end def main print "Enter a number:" num = gets.chomp!.to_i if num >= 1 table = fill_table(num) print_table(table) else puts "Pascal triangle cannot have #{num} rows" end end main 

Ruby Implementation

[Solution] (./Ruby/pascal.rb)

""" @author:aaditkamat @date: 9/1/2019 """ def fill_table(num): table = [] for i in range(num): table.append([0] * num) for i in range(num): table[i][0] = 1 for i in range(1, num): for j in range(1, num): table[i][j] = table[i - 1][j] + table[i - 1][j - 1] return table def print_table(table): str = '' for i in range(len(table)): for j in range(len(table)): if table[i][j] != 0: str += f'{table[i][j]} ' str += '\n' print(str) def main(): print("Enter a number:") num = int(input()) if num >= 1: table = fill_table(num) print_table(table) else: print(f'Pascal triangle cannot have {num} rows') main() 

Java Implementation

Solution

/** * @date 09/01/19 * @author SPREEHA DUTTA */ import java.util.*; public class PascalTriangle { public static int pascal(int r,int c) { if(r==c || c==0) return 1; else return pascal(r-1,c)+pascal(r-1,c-1); } public static void print(int n) { for(int i=0;i<n;i++) { for(int j=0;j<=i;j++) System.out.print(pascal(i,j)+" "); System.out.println(); } } public static void main(String []args) { Scanner sc=new Scanner(System.in); int n; n=sc.nextInt(); print(n); } }