4.9 BST Sequences: partial solution using another approach

Author: amejiarosario

src/trees-and-graphs/bst-sequence.js

@@ -25,39 +25,38 @@ function getSequences(root) {
 /**
  * Weave two arrays with a given prefix
  */
-function weave(prefix = [], array1 = [[]], array2 = [[]]) {
+function weave(prefix = [], arrays1 = [[]], arrays2 = [[]]) {
   let result = [];
 
+  // TODO: validations of prefix as an array and array1/2 as a nested array
+
   // convert prefix to array if is not any
   if(prefix && !Array.isArray(prefix)) {
     prefix = [prefix];
   }
 
-  // return prefix if arrays are empty
-  if((!array1.length && !array2.length) || (!array1.some(subarrayHasSomething) && !array2.some(subarrayHasSomething))) {
-    result.push(prefix);
-  }
+  arrays1.forEach((array1) => {
+    arrays2.forEach((array2) => {
 
-  array1.forEach((a) => {
-    if(a.length) {
-      result = result.concat(weave(prefix.concat(a), [[]], array2));
-    }
-  });
+      if(!array1.length && !array2.length) {
+        result.push(prefix);
 
-  array2.forEach((b) => {
-    if(b.length) {
-      result = result.concat(weave(prefix.concat(b), array1, [[]]));
-    }
+      } else if(!array1.length) {
+        result = result.concat(weave(prefix.concat(array2), [array1]));
+
+      } else if(!array2.length) {
+        result = result.concat(weave(prefix.concat(array1), [array2]));
+      } else {
+        result = result.concat(weave(prefix.concat(array1), [array2]));
+        result = result.concat(weave(prefix.concat(array2), [array1]));
+      }
+    });
   });
 
-  // console.log('\nweave (', prefix, array1, array2, ')');
+  // console.log('\nweave (', prefix, arrays1, arrays2, ')');
   // console.log('\t =>', result);
 
   return result;
 }
 
-function subarrayHasSomething(array) {
-  return array.length;
-}
-
-module.exports = {getSequences, weave};
+module.exports = {getSequences, weave};

src/trees-and-graphs/bst-sequence.spec.js

@@ -11,40 +11,69 @@ describe('weave', function () {
     expect(weave()).to.eql([[]]);
   });
 
-  it('should weave given one array', function () {
+  it('should append to prefix arrays2 if arrays1 is empty', function () {
     expect(weave([2, 1], [[]], [[3]])).to.eql([
       [2, 1, 3]
     ]);
+  });
 
-    expect(weave([2, 3], [[1]])).to.eql([
-      [2, 3, 1]
+  it('should append to prefix arrays1 if arrays2 is empty', function () {
+    expect(weave([2, 3], [[1, 4]])).to.eql([
+      [2, 3, 1, 4]
     ]);
   });
 
   it('should weave given two arrays', function () {
     const prefix = 2;
-    const array1 = [[1]];
-    const array2 = [[3]];
+    const arrays1 = [[1]];
+    const arrays2 = [[3]];
     const weaved = [
       [2, 1, 3],
       [2, 3, 1]
     ];
-    expect(weave(prefix, array1, array2)).to.eql(weaved);
+    expect(weave(prefix, arrays1, arrays2)).to.eql(weaved);
   });
 
-  it.only('should cross array 1 with array 2 keeping the same order', function () {
+  /**
+   * weave(5, [3,2], [8]) = weave([5,3,2], [], [8]) + weave([5, 8], [3,2], [])
+   */
+  it('should cross array 1 with array 2 keeping the same order', function () {
     const prefix = 5;
-    const array1 = [[3, 2]];
-    const array2 = [[8, 6]];
+    const arrays1 = [[3, 2]];
+    const arrays2 = [[8]];
+    const weaved = [
+      [5, 3, 2, 8],
+      [5, 3, 8, 2],
+      [5, 8, 3, 2],
+    ];
+    expect(weave(prefix, arrays1, arrays2)).to.eql(weaved);
+  });
+
+  it('should cross array 2 with array 1 keeping the same order', function () {
+    const prefix = 5;
+    const arrays1 = [[3]];
+    const arrays2 = [[8, 9]];
+    const weaved = [
+      [5, 3, 8, 9],
+      [5, 8, 3, 9],
+      [5, 8, 9, 3],
+    ];
+    expect(weave(prefix, arrays1, arrays2)).to.eql(weaved);
+  });
+
+  it('should cross array 1 with array 2 keeping the same order', function () {
+    const prefix = 5;
+    const arrays1 = [[3, 2]];
+    const arrays2 = [[8, 6]];
     const weaved = [
       [5, 3, 2, 8, 6],
       [5, 3, 8, 2, 6],
       [5, 8, 3, 2, 6],
       [5, 8, 3, 6, 2],
       [5, 8, 6, 3, 2],
     ];
-    expect(weave(prefix, array1, array2)).to.eql(weaved);
-  })
+    expect(weave(prefix, arrays1, arrays2)).to.eql(weaved);
+  });
 });
 
 xdescribe('Graph: BST sequence', function () {