Add Simple Recursion/Nth Factorial (algorithm-visualizer#19)

Author: frankymacster

Simple Recursive/Nth Factorial/README.md

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+# nth Factorial
+Finding nth Factorial using recursion.
+
+## Complexity
+* **Time**: ![](https://latex.codecogs.com/svg.latex?O(2ⁿ))
+* **Space**: ![](https://latex.codecogs.com/svg.latex?O(2ⁿ))
+
+## References
+* [codeburst.io](https://codeburst.io/learn-and-understand-recursion-in-javascript-b588218e87ea)

Simple Recursive/Nth Factorial/code.js

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+// import visualization libraries {
+const { Tracer, Array1DTracer, Layout, VerticalLayout } = require('algorithm-visualizer');
+// }
+
+// define tracer variables {
+var tracer = new Array1DTracer('Sequence');
+Layout.setRoot(new VerticalLayout([tracer]));
+var index = 15;
+var D = [1];
+for (var i = 1; i < index; i++) {
+  D.push(0);
+}
+tracer.set(D);
+Tracer.delay();
+// }
+
+function fact(num) {
+  if (num < 0) {
+    return;
+  }
+
+  if (num === 0) {
+    return 1;
+  }
+
+  var res = num * fact(num - 1);
+
+  D[num - 1] = res;
+  
+  // visualize {
+  tracer.select(num - 1);
+  Tracer.delay();
+  tracer.patch(num - 1, D[num - 1]);
+  Tracer.delay();
+  tracer.depatch(num - 1);
+  tracer.deselect(num - 1);
+  // }
+
+  return res;
+}
+fact(index);