added frequency counter algorithm based problems.

src/algorithms/Fequency Counter based/Anagrams.js

@@ -0,0 +1,45 @@
+//program to check if two hard-coded strings are anagrams or not.
+
+function isAnagram(str1, str2) {
+
+//firstly, they need to be of the same length.
+    if (str1.length !== str2.length) {
+        return false;
+    }
+
+//frequency counters
+    var frequencyCounter1 = {}
+      , frequencyCounter2 = {};
+
+//value of frequency counter being updated for every string character.
+/*what this actually does is, it creates an object, in which the key value pairs are as follows -->
+
+      key : value :: character : frequency
+
+*/
+
+//added, toLowerCase() method to make it case insensitive.
+    for (let val of str1.toLowerCase()) {
+        frequencyCounter1[val] = (frequencyCounter1[val] || 0) + 1;
+    }
+
+    for (let val of str2.toLowerCase()) {
+        frequencyCounter2[val] = (frequencyCounter2[val] || 0) + 1;
+    }
+
+    for (let key in frequencyCounter1) {
+        //checks if the particular key exists or not
+        if (!(key in frequencyCounter2)) {
+            return false;
+        }
+
+        //then checks, if for the particular keys of the two objects, the values are equal or not.
+        if (frequencyCounter2[key] !== frequencyCounter1[key]) {
+            return false;
+        }
+    }
+    return true;
+}
+
+//Remember Shutter Island :P
+isAnagram("Rachel Solando", "Dolores Chanal");

src/algorithms/Fequency Counter based/areEqualNoOfSquares.js

@@ -0,0 +1,40 @@
+//Program to check if the elements in the second array, are the squares of each and every element of the first array.
+function areEqualNoOfSqs(arr1, arr2) {
+
+//firstly, they need to be of the same length.
+
+    if (arr1.length !== arr2.length) {
+        return false;
+    }
+
+//frequency counters
+    var freqCounter1 = {}
+      , freqCounter2 = {};
+
+//value of frequency counter being updated for every string character.
+/*what this actually does is, it creates an object, in which the key value pairs are as follows -->
+
+      key : value :: character : frequency
+
+*/
+    for (let val of arr1) {
+        freqCounter1[val] = (freqCounter1[val] || 0) + 1;
+    }
+
+    for (let val of arr2) {
+        freqCounter2[val] = (freqCounter2[val] || 0) + 1;
+    }
+
+    for (let key in freqCounter1) {
+        if (!(key ** 2 in freqCounter2)) {
+            return false;
+        }
+
+        if (freqCounter2[key ** 2] !== freqCounter1[key]) {
+            return false;
+        }
+    }
+    return true;
+}
+
+areEqualNoOfSqs([2, 3, 4, 1, 2, 5], [25, 4, 9, 1, 4, 16]);

src/algorithms/Fequency Counter based/areThereDuplicates_FQ.js

@@ -0,0 +1,17 @@
+
+//Program to check if duplicate elements are present inside an array.
+
+function areThereDuplicatesFQ(){
+    let obj = {};
+
+    for(let val in arguments){
+        obj[arguments[val]] = (obj[arguments[val]]||0)+1;
+    }
+
+    for(let key in obj){
+        if(obj[key]>1) return true;
+    }
+    return false;
+}
+
+areThereDuplicatesFQ(1,2,5,7,8);

src/algorithms/Fequency Counter based/sameFrequency.js

@@ -0,0 +1,37 @@
+//Numeric anagrams detector
+
+function sameFrequency(strA, strB) {
+
+//convert the array, into a string
+    var str1 = strA.toString()
+      , str2 = strB.toString();
+
+    if (str1.length !== str2.length) {
+        return false;
+    }
+
+    var freqCounter1 = {}
+      , freqCounter2 = {};
+
+
+    for (let val of str1) {
+        freqCounter1[val] = (freqCounter1[val] || 0) + 1;
+    }
+
+    for (let val of str2) {
+        freqCounter2[val] = (freqCounter2[val] || 0) + 1;
+    }
+
+    for (let key in freqCounter1) {
+        if (!(key in freqCounter2)) {
+            return false;
+        }
+
+        if (freqCounter2[key] !== freqCounter1[key]) {
+            return false;
+        }
+    }
+    return true;
+}
+
+sameFrequency(552181, 152581);