fixes: #1280 and test: added tests for DFS algorithm (#1303)

* fix: fixed error in DepthFirstSearch algorithm and test: added tests for DepthFirstSearch algorithm.

* changed traverseDFS function parameters in DepthFirstSearch.js file

Trees/DepthFirstSearch.js

@@ -4,35 +4,32 @@
  * DFS Algorithm for traversing or searching graph data structures.
 */
 
-function traverseDFS (root) {
-  const stack = [root]
+// traverses a give tree from specified root's value
+function traverseDFS (tree, rootValue) {
+  const stack = []
   const res = []
-
+  stack.push(searchDFS(tree, rootValue))
+  // if root is not present in the tree, returning empty array
+  if (!stack[0]) return res
   while (stack.length) {
     const curr = stack.pop()
-    res.push(curr.key)
-
-    if (curr.right) {
-      stack.push(curr.right)
-    }
-
+    res.push(curr.value)
     if (curr.left) {
-      stack.push(curr.left)
+      stack.push(tree[curr.left])
+    }
+    if (curr.right) {
+      stack.push(tree[curr.right])
     }
   }
-
   return res.reverse()
 }
 
 function searchDFS (tree, value) {
   const stack = []
-
   stack.push(tree[0])
-
   while (stack.length !== 0) {
     for (let i = 0; i < stack.length; i++) {
       const node = stack.pop()
-
       if (node.value === value) {
         return node
       }
@@ -59,11 +56,10 @@ const tree = [
   { value: 10, left: null, right: null },
   { value: 1, left: null, right: null }
 ]
-
-searchDFS(tree, 9)
-searchDFS(tree, 10)
-
-traverseDFS(6)
+searchDFS(tree, 9) // { value: 9, left: 7, right: 8 }
+searchDFS(tree, 200) // null
+traverseDFS(tree, 6) // [ 1, 2, 3, 4, 5, 8, 10, 9, 7, 6 ]
+traverseDFS(tree, 200) // []
 
 //            6
 //           / \
@@ -74,3 +70,4 @@ traverseDFS(6)
 //      2       8   10
 //     /
 //    1
+export { searchDFS, traverseDFS }

Trees/test/DepthFirstSearch.test.js

@@ -0,0 +1,46 @@
+import { searchDFS, traverseDFS } from '../DepthFirstSearch'
+
+describe('Depth First Tree Traversal', () => {
+  const tree = [
+    { value: 6, left: 1, right: 2 },
+    { value: 5, left: 3, right: 4 },
+    { value: 7, left: null, right: 5 },
+    { value: 3, left: 6, right: null },
+    { value: 4, left: null, right: null },
+    { value: 9, left: 7, right: 8 },
+    { value: 2, left: 9, right: null },
+    { value: 8, left: null, right: null },
+    { value: 10, left: null, right: null },
+    { value: 1, left: null, right: null }
+  ]
+
+  //            6
+  //           / \
+  //          5   7
+  //         / \   \
+  //        3   4   9
+  //       /       / \
+  //      2       8   10
+  //     /
+  //    1
+
+  it('should be null if given value is not present in the tree - DF Search', () => {
+    const res = searchDFS(tree, 200)
+    expect(res).toStrictEqual(null)
+  })
+
+  it('should return the node if given value is present in the tree - DF Search', () => {
+    const res = searchDFS(tree, 9)
+    expect(res).toStrictEqual({ value: 9, left: 7, right: 8 })
+  })
+
+  it('should return empty array if given root is not present in the tree - DF Traversal', () => {
+    const traversal = traverseDFS(tree, 200)
+    expect(traversal).toStrictEqual([])
+  })
+
+  it('should return DFT array of given tree from specified root if given root is present in the tree - DF Traversal', () => {
+    const traversal = traverseDFS(tree, 6)
+    expect(traversal).toStrictEqual([1, 2, 3, 4, 5, 8, 10, 9, 7, 6])
+  })
+})