Create print-pascals-pyramid.rs (#4936)

Print-pascals-pyramid closes issue #2968

program/program/print-pascals-triangle/print-pascals-pyramid.rs

@@ -0,0 +1,53 @@
+//Rust program to print pascal's triangle
+//
+//Pascal's triangle is a triangular array of the binomial coefficients. Write a function that takes an
+// integer value n as input and prints first n lines of the Pascal's triangle.
+//
+//Input  : 5
+//
+//Output : 
+//        1
+//       1 1
+//      1 2 1
+//     1 3 3 1
+//    1 4 6 4 1
+
+use std::io;
+
+fn print_pascals_triangle(levels: u32)
+{
+
+	// outer loop to go through all the levels
+  	for row in 0..levels {
+
+    		let mut print_num = 1;	//start every row with "1"
+
+    		//print spaces out before row based on num of levels
+
+    		for _j in 1..2*(levels-1-row)+1 {
+      		print!(" ");
+    		}
+
+    		// calculate binomial coefficients ==> p = p * ((row-col)/(col+1))
+
+    		for calc_col in 0..row+1 {
+      			print!("{:3} ", print_num);
+      			print_num = print_num * (row-calc_col)/(calc_col+1);
+    		}
+
+    		println!(); //insert a newline to start the next line to print
+  	}
+}
+
+fn main() {
+
+	// the input string and this main function can be removed. This is simply for testing
+
+	println!("Enter the number of levels to print");
+	let mut input_num = String::new();
+	let _rtrn = io::stdin().read_line(&mut input_num);
+	let n: u32 = input_num.trim().parse().expect("Input not an integer");	
+
+	// example of how to call the function and print out the results of the inverted pyramid.
+    	print_pascals_triangle(n);
+}