From f40115ff3beb9bb0c90ce657c3b3da3b26ad2900 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Wed, 6 Dec 2017 23:50:23 +0200
Subject: [PATCH] Swap, anagrams, occurences

Fixed sorting title for strings.
---
 README.md                                     | 38 ++++++++++++++++++-
 .../anagrams-of-string-(with-duplicates).md   | 16 ++++++++
 .../count-occurences-of-a-value-in-array.md   |  7 ++++
 ...rt-characters-in-string-(alphabetical).md} |  0
 snippets/swap-values-of-two-variables.md      |  7 ++++
 5 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 snippets/anagrams-of-string-(with-duplicates).md
 create mode 100644 snippets/count-occurences-of-a-value-in-array.md
 rename snippets/{sort-characters-in-string-alphabetical.md => sort-characters-in-string-(alphabetical).md} (100%)
 create mode 100644 snippets/swap-values-of-two-variables.md

diff --git a/README.md b/README.md
index fe47fbade..958fc1722 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,8 @@
 
 ## Contents
 
+* [Anagrams of string (with duplicates)](#anagrams-of-string-with-duplicates)
+* [Count occurences of a value in array](#count-occurences-of-a-value-in-array)
 * [Even or odd number](#even-or-odd-number)
 * [Fibonacci array generator](#fibonacci-array-generator)
 * [Greatest common divisor (GCD)](#greatest-common-divisor-gcd)
@@ -15,10 +17,36 @@
 * [Random number in range](#random-number-in-range)
 * [Randomize order of array](#randomize-order-of-array)
 * [RGB to hexadecimal](#rgb-to-hexadecimal)
-* [Sort characters in string alphabetical](#sort-characters-in-string-alphabetical)
+* [Sort characters in string (alphabetical)](#sort-characters-in-string-alphabetical)
 * [Sum of array of numbers](#sum-of-array-of-numbers)
+* [Swap values of two variables](#swap-values-of-two-variables)
 * [Unique values of array](#unique-values-of-array)
 
+### Anagrams of string (with duplicates)
+
+Use recursion.
+For each letter in the given string, create all the partial anagrams for the rest of its letters.
+Use `map()` to combine the letter with each partial anagram, then `reduce()` to combine all anagrams in one array.
+Base cases are for string `length` equal to `2` or `1`.
+
+```js
+var anagrams = s => {
+  if(s.length <= 2)  return s.length === 2 ? [s, s[1] + s[0]] : [s];
+  return s.split('').reduce( (a,l,i) => {
+    anagrams(s.slice(0,i) + s.slice(i+1)).map( v => a.push(l+v) );
+    return a;
+  }, []);
+}
+```
+
+### Count occurences of a value in array
+
+Use `filter()` to create an array containing only the items with the specified value, count them using `length`.
+
+```js
+var countOccurences = (arr, value) => arr.filter(v => v === value).length;
+```
+
 ### Even or odd number
 
 Use `Math.abs()` to extend logic to negative numbers, check using the modulo (`%`) operator.
@@ -106,6 +134,14 @@ var sum = arr =>
   arr.reduce( (acc , val) => acc + val, 0);
 ```
 
+### Swap values of two variables
+
+Use array destructuring to swap values between two variables.
+
+```js
+[varA, varB] = [varB, varA];
+```
+
 ### Unique values of array
 
 Use `reduce()` to accumulate all unique values in an array.
diff --git a/snippets/anagrams-of-string-(with-duplicates).md b/snippets/anagrams-of-string-(with-duplicates).md
new file mode 100644
index 000000000..9c13eed58
--- /dev/null
+++ b/snippets/anagrams-of-string-(with-duplicates).md
@@ -0,0 +1,16 @@
+### Anagrams of string (with duplicates)
+
+Use recursion.
+For each letter in the given string, create all the partial anagrams for the rest of its letters.
+Use `map()` to combine the letter with each partial anagram, then `reduce()` to combine all anagrams in one array.
+Base cases are for string `length` equal to `2` or `1`.
+
+```js
+var anagrams = s => {
+  if(s.length <= 2)  return s.length === 2 ? [s, s[1] + s[0]] : [s];
+  return s.split('').reduce( (a,l,i) => {
+    anagrams(s.slice(0,i) + s.slice(i+1)).map( v => a.push(l+v) );
+    return a;
+  }, []);
+}
+```
diff --git a/snippets/count-occurences-of-a-value-in-array.md b/snippets/count-occurences-of-a-value-in-array.md
new file mode 100644
index 000000000..6851c33bf
--- /dev/null
+++ b/snippets/count-occurences-of-a-value-in-array.md
@@ -0,0 +1,7 @@
+### Count occurences of a value in array
+
+Use `filter()` to create an array containing only the items with the specified value, count them using `length`.
+
+```js
+var countOccurences = (arr, value) => arr.filter(v => v === value).length;
+```
diff --git a/snippets/sort-characters-in-string-alphabetical.md b/snippets/sort-characters-in-string-(alphabetical).md
similarity index 100%
rename from snippets/sort-characters-in-string-alphabetical.md
rename to snippets/sort-characters-in-string-(alphabetical).md
diff --git a/snippets/swap-values-of-two-variables.md b/snippets/swap-values-of-two-variables.md
new file mode 100644
index 000000000..d1cd017b9
--- /dev/null
+++ b/snippets/swap-values-of-two-variables.md
@@ -0,0 +1,7 @@
+### Swap values of two variables
+
+Use array destructuring to swap values between two variables.
+
+```js
+[varA, varB] = [varB, varA];
+```