Week4a Algorithm

04week/algorithms.js

@@ -9,22 +9,135 @@ function getRandomInt(min, max) {
 }
 
 let arr = [];
+let flip = false;
 
-for (let i = 0; i < 1000; i++) {
-  arr.push(getRandomInt(0, 1000));
+for (let i = 0; i < 10; i++) {
+  arr.push(getRandomInt(0, 100));
 }
 
-function bubbleSort(arr) {
-  // Your code here
+function bubbleSort(ary) {
+  /*********************** WHITE BOARD NOTES **************************
+  // Using bubble sort alrgorithm to sort passed array.
+  // set flip flag equal to false
+  // Loop through array
+  //   Compare array[n] to array[n+1]
+  //   if array[n] is larger, then flip
+  //   set flip flag equal to true.
+  // End Loop
+  // if flip flag = true
+  //   set flip flag back to false
+  //   return bubbleSort(arr)
+  // else // array should be sorted
+  //   return arr
+  // end if
+  ********************************************************************/
+
+  for (let i = 0; i< ary.length; i++){
+    if (ary[i] > ary[i + 1]) {
+      flip = true;
+      // using the swap without temp algorithm!  Ex: ary[i] = 10, ary[i+1] = 6
+      ary[i+1] = ary[i+1] - ary[i];  //Ex. 6 - 10 = -4
+      ary[i]   = ary[i] + ary[i+1];  //Ex.  10 + (-4) = 6
+      ary[i+1] = ary[i] - ary[i+1];  //Ex.  6 - (-4) = 10
+    }
+  }
+  // flip? (flip = false, return bubbleSort(ary)) : return(ary); // doesn't work.
+  if (flip) {
+    flip = false;  // setting my check
+    return bubbleSort(ary);
+  } else {
+    return ary;
+  }
+}
+
+console.log('Bubble Sort');
+console.log(arr);
+console.log(bubbleSort(arr));
+
+function mergeSort(ary) {
+  /*********************** WHITE BOARD NOTES **************************
+  // Merge sort is a recursive algorithm.
+  // It is a divide in half approach.  Keep dviding until you get to
+  // only 1 element on either the left or right side.
+  // Now call merge.  Merge compares the two sub arrays and orders them.
+  // Ultimately, you get back to 2 sorted sub-arrays.  Merge will finally order them.
+  ********************************************************************/
+  if (ary.length < 2) return ary;
+
+  const middle = Math.floor(ary.length / 2);
+  const leftSide = ary.slice(0, middle);
+  const rightSide = ary.slice(middle);
+
+  return merge(mergeSort(leftSide), mergeSort(rightSide));
 }
 
-function mergeSort(arr) {
-  // Your code here
+function merge (left, right) {
+  let result = [];
+  while (left.length && right.length)
+    result.push(left[0] < right[0]? left.shift() : right.shift());
+  return result.concat(left.length? left : right);
 }
 
-function binarySearch(arr, item) {
-  // Your code here
+// Adding 10 more random values to array.
+for (let i = 0; i < 10; i++) {
+  arr.push(getRandomInt(0, 100));
 }
+console.log('Merge Sort');
+console.log(arr);
+arr = mergeSort(arr);
+console.log(arr);
+
+function binarySearch(ary, item, start=0, end = ary.length-1) {
+  /*********************** WHITE BOARD NOTES **************************
+  // Assumptions...
+  // You are given a sorted data array to search on.
+  // Given a value to search for...
+  // ****** DID NOT WORK!  ARRAY IS BROKEN DOWN UNTIL VALUE IS 0 ELEMENT *****
+  // Binary Search.
+  //   Locate the middle of the data array
+  //   Compare search value with middle.
+  //   If search value = middle value then
+  //     Congrats youfound it!
+  //     return index position in array.
+  //   else if search value < middle value
+  //     Change array to be subArray[0 - middle value-1]
+  //     return binarySearch[subArray]
+  //   else if search value > middle value then
+  //     Change array to be subArray[0 - middle value-1]
+  //     Change array to be subArray[middle value+1 - endArray.]
+  //     return binarySearch[subArray]
+  //   end if
+  //   return -1 // did not find the search value in the data array
+  // *** RESEARCHED.  FOUND RECURSIVE EXAMPLE PASSING IN START, END *********
+  //   Keep array intact (no splice, slice).  Pass in start, end search elements.
+  //   Locate the middle of the data array
+  //   Compare search value with middle.
+  //   If search value = middle value then
+  //     Congrats youfound it!
+  //     return index position in array.
+  //   else if start element = end element then
+  //     return false.  Value not in array
+  //   else if search value < middle value
+  //     Change end search = middle-1
+  //     return binarySearch(array, item, start end)
+  //   else if search value > middle value then
+  //     Change start search = middle+1
+  //     return binarySearch(array, item, start end)
+  //   end if
+  ********************************************************************/
+
+  const middle = Math.floor(start + (end-start)/2);  // find the halfway position in array
+  // console.log(start, end, middle, ary[middle]);
+  if (item == ary[middle]) return middle;   // Congrats. you found the item.
+  else if (start>=end) return false;  // item not in array
+  else if (item < ary[middle]) return binarySearch(ary, item, start, middle-1);  // item in lower half
+  else if (item > ary[middle]) return binarySearch(ary, item, middle+1, end);  // item in upper half
+}
+
+console.log('Binary Search');
+console.log(arr);
+console.log(`Looking for 42.  It is here: ${binarySearch(arr, 42)}`);
+// console.log(binarySearch(arr, 42));
 
 // Tests
 
@@ -61,8 +174,4 @@ if (typeof describe === 'function') {
     });
   });
 
-} else {
-
-  console.log('Run the tests!')
-
 }