Merge pull request #26 from rroque98/refactorSolutionsChap1

Refactor JavaScript Solutions to 1.2, 1.3, 1.4, 1.6

Author: fvntr

JavaScript/chapter01/1.2 - Check Perm/rroque98_sol.js

@@ -1,37 +1,34 @@
 /*Given two strings, write a method to decide
 if one is apermutation of the other permutation:*/
 
-const isPermutation = (str1, str2) =>{
+const isPermutation = (str1, str2) => {
   if (str1.length !== str2.length) {
     return false;
   }
-  const obj1 = determineCharCount(str1);
-  const obj2 = determineCharCount(str2);
-  for (let char of str1) {
-    if (obj1[char] !== obj2[char]) {
+  const freq1 = determineCharCount(str1);
+  const freq2 = determineCharCount(str2);
+  for (const [char, count] of freq1) {
+    if (count !== freq2.get(char)) {
       return false;
     }
   }
   return true;
   //******** helper function ******
   function determineCharCount(string) {
-    const obj = {};
-    for (let char of string) {
-      if (obj[char] !== undefined) {
-        obj[char]++;
-      } else {
-        obj[char] = 1;
-      }
-    }
-    return obj;
+    return string
+      .split('')
+      .reduce(
+        (acc, char) => acc.set(char, (acc.get(char) || 0) + 1),
+        new Map()
+      );
   }
-}
+};
 
 // Tests:
-  console.log(isPermutation('abc', 'abb') === false);
-  console.log(isPermutation('abb', 'abc') === false);
-  console.log(isPermutation('aaa', 'abc') === false);
-  console.log(isPermutation('abc', 'abcd') === false);
-  console.log(isPermutation('abc', 'bac') === true);
-  console.log(isPermutation('', '') === true);
-  console.log(isPermutation('12', '21') === true);
+console.log(isPermutation('abc', 'abb') === false);
+console.log(isPermutation('abb', 'abc') === false);
+console.log(isPermutation('aaa', 'abc') === false);
+console.log(isPermutation('abc', 'abcd') === false);
+console.log(isPermutation('abc', 'bac') === true);
+console.log(isPermutation('', '') === true);
+console.log(isPermutation('12', '21') === true);

JavaScript/chapter01/1.3 - URLify/rroque98_sol.js

@@ -1,8 +1,8 @@
 // Write a method to replace all spaces within a string with '%20'
 
-const URLify = (string) => string.split(' ').join('%20');
+const encodeSpaces = (string) => string.replace(/ /g, '%20');
 
 // Tests:
-console.log(URLify('Hello World') === 'Hello%20World');
-console.log(URLify('') === '');
-console.log(URLify('This is an example') === 'This%20is%20an%20example');
+console.log(encodeSpaces('Hello World') === 'Hello%20World');
+console.log(encodeSpaces('') === '');
+console.log(encodeSpaces('This is an example') === 'This%20is%20an%20example');

JavaScript/chapter01/1.4 - PalinPerm/rroque98_sol.js

@@ -1,20 +1,17 @@
 // Given a string, write a function to check if it is a permutation of a palindrome
 
 const isPalindromePermutation = (str) => {
-  const strNoSpaces = str.split(' ').join('');
-  const obj = {};
+  const strNoSpaces = str.replace(/ /g, '');
   var oddCount = 0;
+  const frequencies = new Map();
   for (let char of strNoSpaces) {
-    if (obj[char] !== undefined) {
-      obj[char]++;
-    } else {
-      obj[char] = 1;
-    }
+    frequencies.set(char, 1 + (frequencies.get(char) || 0));
   }
-  for (let key in obj) {
-    if (obj[key] % 2) {
-      oddCount++;
+  for (let frequency of frequencies.values()) {
+    if (frequency % 2 === 0) {
+     continue;
     }
+    oddCount++;
     if (oddCount > 1) {
       return false;
     }

JavaScript/chapter01/1.6 - String Compression/rroque98_sol.js

@@ -1,33 +1,38 @@
-/* Implement a method to perform basic string 
-compression using the counts of repeated characters
+/* Implement a method to perform basic string
+compression using the counts of repeated characters.
+If the compressed string length is more than original
+string length, return original string.
 Ex: 'aabcccccaaa' would become a2b1c5a3
 */
 
 const stringCompression = (str) => {
   if (!str.length) {
     return '';
   }
-  var compStr = '';
-  var count = 1;
-  var currentChar = str[0];
-  for (let i = 1; i < str.length; i++) {
+  let compStr = '';
+  let count = 0;
+  let currentChar = str[0];
+  for (let i = 0; i < str.length; i++) {
     let char = str[i];
     if (char === currentChar) {
       count++;
-      if (i === str.length - 1) {
-        compStr += `${currentChar}${count}`;
-      }
     } else {
       compStr += `${currentChar}${count}`;
       currentChar = char;
       count = 1;
     }
   }
+  compStr += `${currentChar}${count}`;
+  if (compStr.length > str.length) {
+    return str;
+  }
   return compStr;
 }
 
 // TESTS
 console.log(stringCompression('aabcccccaaa') === 'a2b1c5a3');
 console.log(stringCompression('cccccccc') === 'c8');
 console.log(stringCompression('') === '');
-console.log(stringCompression('AabccCccaaa') === 'A1a1b1c2C1c2a3');
+console.log(stringCompression('AabccCccaaa') === 'AabccCccaaa');
+// Explanation: 'A1a1b1c2C1c2a3' length is longer than original string so returns original string
+console.log(stringCompression('x') === 'x');