use a different approach for reverse words in a string, and correct some previous implementations

Author: beck chen

leetcode practice/array and strings/reverseWordsInAString2.js

@@ -10,30 +10,30 @@
  * @param {character[]} str
  * @return {void} Do not return anything, modify str in-place instead.
  */
-var reverseWords = function (str) {
-    reverseChars(str, 0, str.length - 1);
+var reverseWords = function (s) {
+    let startIndex = 0;
+    while (s[startIndex] === ' ') {
+        startIndex++;
+    }
+
+    let endIndex = s.length - 1;
+    while (s[endIndex] === ' ') {
+        endIndex--;
+    }
 
-    // loop from beginning of arr to second to last character,
-    // look for start of string, and look for space, and 
-    // reverse the characters in between 
-    let wordStartIndex = 0;
-    for (let ii = 0; ii < str.length - 1; ii++) {
-        if (str[ii + 1] === ' ') {
-            reverseChars(str, wordStartIndex, ii);
-            wordStartIndex = ii + 2;
+    let word = '';
+    const wordsArr = [];
+    for (let charIndex = startIndex; charIndex <= endIndex; charIndex++) {
+        if (s[charIndex] !== ' ') {
+            word += s[charIndex];
+        } else if (word.length !== 0 && s[charIndex] === ' ') {
+            wordsArr.unshift(word);
+            word = '';
         }
     }
 
-    // reverse the last word
-    reverseChars(str, wordStartIndex, str.length - 1);
-    return str;
-};
+    // dont forget about the last word
+    wordsArr.unshift(word);
 
-function reverseChars(wordsToReverseArr, firstIndex, lastIndex) {
-    while (firstIndex < lastIndex) {
-        [wordsToReverseArr[firstIndex], wordsToReverseArr[lastIndex]]
-            = [wordsToReverseArr[lastIndex], wordsToReverseArr[firstIndex]];
-        firstIndex++;
-        lastIndex--;
-    }
-}
+    return wordsArr.join(' ');
+};

leetcode practice/array and strings/spiralMatrix.js

@@ -0,0 +1,41 @@
+/**
+ * @param {number[][]} matrix
+ * @return {number[]}
+ */
+var spiralOrder = function (matrix) {
+    const printArr = [];
+    if (matrix.length === 0) { return printArr; }
+
+    let firstRow = 0, lastRow = matrix.length - 1,
+        firstCol = 0, lastCol = matrix[0].length - 1;
+
+    while (lastRow >= firstRow && lastCol >= firstCol) {
+        // add top
+        for (let colIndex = firstCol; colIndex <= lastCol; colIndex++) {
+            printArr.push(matrix[firstRow][colIndex]);
+        }
+
+        // add right
+        for (let rowIndex = firstRow + 1; rowIndex <= lastRow; rowIndex++) {
+            printArr.push(matrix[rowIndex][lastCol]);
+        }
+
+        if (lastRow > firstRow && lastCol > firstCol) {
+            // add bottom
+            for (let colIndex = lastCol - 1; colIndex > firstCol; colIndex--) {
+                printArr.push(matrix[lastRow][colIndex]);
+            }
+
+            for (let rowIndex = lastRow; rowIndex > firstRow; rowIndex--) {
+                printArr.push(matrix[rowIndex][firstCol]);
+            }
+        }
+
+        firstRow++;
+        lastRow--;
+        firstCol++;
+        lastCol--;
+    }
+
+    return printArr;
+}

sessions/array and strings/printElementOfMatrixInSpiralOrder.js

@@ -21,6 +21,13 @@ function printElementsInLayer(matrix, layerIndex) {
         firstRow = layerIndex,
         lastRow = matrix.length - 1 - layerIndex;
 
+    // in the case where we're at the center-most layer, and that layer only
+    // has one element, we should just print it
+    if (lastRow === layerIndex && lastColumm === layerIndex) {
+        console.log(matrix[layerIndex][layerIndex]);
+        return;
+    }
+
     // print top
     // note that this does not include the rightmost element of the first row.
     // that element belongs to the right column
@@ -51,4 +58,5 @@ function printElementsInLayer(matrix, layerIndex) {
 }
 
 // this should print 2, 3, 1, 6, 7, 9, 11, 4, 8, 12, 13, 5
-console.log(printElementsSpiralOrder([[2, 3, 1, 6], [12, 13, 5, 7], [8, 4, 11, 9]]));
+// console.log(printElementsSpiralOrder([[2, 3, 1, 6], [12, 13, 5, 7], [8, 4, 11, 9]]));
+console.log(printElementsSpiralOrder([[6, 9, 7]]));

sessions/array and strings/rotate2DArray.js

@@ -20,7 +20,7 @@ function rotateMatrix(matrix) {
 function rotateLayerOfMatrix(matrix, layerIndex) {
     const startIndex = layerIndex;
     const endIndex = matrix.length - 1 - layerIndex; // ex. for a 5 x 5 matrix, layer 1 ends at 5 - 1 - 1 = 3
-    for (let ii = startIndex; ii < endIndex; ii++) {
+    for (let ii = 0; ii < endIndex - startIndex; ii++) {
         // store top element
         const storedTopElem = matrix[startIndex][startIndex + ii];
         // rotate left to top