Add Pascal's triangle. (#149)

* Add Pascal's triangle.

* Update pascalTriangle.js

* Update pascalTriangle.js

Co-authored-by: vinayak <itssvinayak@gmail.com>

maths/pascalTriangle.js

@@ -0,0 +1,31 @@
+const numRows = 5                                                                                                                                      
+
+var generate = function (numRows) {
+  const triangle = [[1], [1, 1]]
+
+  if (numRows === 0) {
+    return []
+  } else if (numRows === 1) {
+    return [[1]]
+  } else if (numRows === 2) {
+    return [[1], [1, 1]]
+  } else {
+    for (let i = 2; i < numRows; i++) {
+      addRow(triangle)
+    }
+  }
+  return triangle
+}
+var addRow = function (triangle) {
+  const previous = triangle[triangle.length - 1]
+  const newRow = [1]
+  for (let i = 0; i < previous.length - 1; i++) {
+    const current = previous[i]
+    const next = previous[i + 1]
+    newRow.push(current + next)
+  }
+  newRow.push(1)
+  return triangle.push(newRow)
+}
+
+generate(numRows)