Add day 18

Author: MadhavBahl

README.md

@@ -34,6 +34,7 @@ Read [CONTRIBUTING.md](./CONTRIBUTING.md) for contribution guidelines.
 15. [Day 15 -- Pascal's Triangle](./day15) -- [http://codetoexpress.tech/dc/day15/](http://codetoexpress.tech/dc/day15/)
 16. [Day 16 -- Tower of Hanoi](./day16) -- [http://codetoexpress.tech/dc/day16/](http://codetoexpress.tech/dc/day16/)
 17. [Day 17 -- N Queens Problem](./day17) -- [http://codetoexpress.tech/dc/day17/](http://codetoexpress.tech/dc/day17/)
+18. [Day 18 -- Frequency Count and Check Power N](./day18) -- [http://codetoexpress.tech/dc/day18/](http://codetoexpress.tech/dc/day18/)
 
 ## [More Problems](./BONUS/README.md)
 

day18/JavaScript/checkPowerN_madhav.js

@@ -0,0 +1,35 @@
+/**
+ * @author MadhavBahlMD
+ * @date 14/01/2019
+ * Using frequency counter
+ */
+
+function checkPowerN (arr1, arr2, num) {
+    if (arr1.length !== arr2.length)    return false;
+
+    let freq1 = {};
+        freq2 = {};
+    
+    // Make frequency counter for array 1
+    let powElement;
+    for (let element of arr1) {
+        powElement = Math.pow (element, num);
+        freq1[powElement] = (freq1[powElement] || 0) + 1;
+    }
+
+    // Make frequency counter for array 2
+    for (let element of arr2) 
+        freq2[element] = (freq2[element] || 0) + 1;
+        
+    // Compare the objects
+    for (let key in freq1) {
+        if (!(key in freq2))
+            return false;
+        if (freq1[key] !== freq2[key])
+            return false;
+    }
+    return true;
+}
+
+console.log (checkPowerN ([1, 2, 3, 4], [4, 9, 1, 16], 2));
+console.log (checkPowerN ([3, 4, 5, 2], [1, 2, 3], 4));

day18/JavaScript/checkPowerN_madhav2.js

@@ -0,0 +1,25 @@
+/**
+ * @author MadhavBahlMD
+ * @date 14/01/2019
+ * Using Brute Force Search
+ */
+
+function checkPowerN (arr1, arr2, num) {
+    if (arr1.length !== arr2.length)    return false;
+
+    for (let i=0; i<arr1.length; i++)
+        arr1[i] = Math.pow (arr1[i], num);
+
+    for (let element of arr1) {
+        let pos = arr2.indexOf (element);
+
+        if (pos < 0)
+            return false;
+        
+        arr2.splice (pos, 1);
+    }
+    return true;
+}
+
+console.log (checkPowerN ([1, 2, 3, 4], [4, 9, 1, 16], 2));
+console.log (checkPowerN ([3, 4, 5, 2], [1, 2, 3], 4));

day18/JavaScript/countUniques1.js

@@ -0,0 +1,24 @@
+/**
+ * @author MadhavBahlMD
+ * @date 14/01/2019
+ * Count uniques using multiple pointers (since the input array is sorted)
+ */
+
+
+function countUniques (arr) {
+    if (arr.length === 0)   return 0;
+
+    let i=0;
+
+    for (let j=1; j<arr.length; j++) {
+        if (arr[i] !== arr[j]) {
+            i++;
+            arr[i] = arr[j];
+        }
+    }
+
+    return i+1;
+}
+
+console.log (`Number of unique elements = ${countUniques([1, 1, 2, 2, 2, 3, 4, 4, 4, 4, 4, 5, 5, 5, 6, 7])}`);
+console.log (`Number of unique elements = ${countUniques([])}`);

day18/JavaScript/countUniques2.js

@@ -0,0 +1,23 @@
+/**
+ * @author MadhavBahlMD
+ * @date 14/01/2019
+ * Count Uniques using frequency object
+ */
+
+function countUniques (arr) {
+    let freq = {},
+        count = 0;
+    
+    for (let element of arr) {
+        if (!(element in freq)) {
+            count++;
+            freq[element] = 1;
+        } else
+            freq[element]++;
+    }
+
+    return count;
+}
+
+console.log (`Number of unique elements = ${countUniques([1, 1, 2, 2, 2, 3, 4, 4, 4, 4, 4, 5, 5, 5, 6, 7])}`);
+console.log (`Number of unique elements = ${countUniques([])}`);

day18/JavaScript/countUniques3.js

@@ -0,0 +1,27 @@
+/**
+ * @author MadhavBahlMD
+ * @date 14/01/2019
+ * Count Uniques using brute force search
+ */
+
+function countUniques (arr) {
+    if (arr.length === 0)   return 0;
+
+    let count = 1; // first element is always unique, since there is nothing behind it
+    for (let j=1; j<arr.length; j++) {
+        let flag = true;
+        for (let i=0; i<j; i++) {
+            if (arr[i] === arr[j]) {
+                flag = false;
+                break;
+            }
+        }
+        if (flag)
+            count++;
+    }
+
+    return count;
+}
+
+console.log (`Number of unique elements = ${countUniques([1, 1, 2, 2, 2, 3, 4, 4, 4, 4, 4, 5, 5, 5, 6, 7])}`);
+console.log (`Number of unique elements = ${countUniques([])}`);

day18/JavaScript/freqCounter_madhav.js

@@ -0,0 +1,24 @@
+/**
+ * @author MadhavBahlMD
+ * @date 01/14/2018
+ * Frequency Ccounter using object
+ */
+
+function freqCounter (arr) {
+    let freq = {};
+
+    // Iterate over the array and update frequency object
+    for (let element of arr) {
+        freq[element] = (freq[element] || 0) + 1;
+    }
+    
+    // Print the output
+    printFrequency (freq);
+}
+
+function printFrequency (freqObj) {
+    for (let key in freqObj)
+        console.log (`'${key}' is present ${freqObj[key]} time(s)`);
+}
+
+freqCounter ([ 1, 2, 3, 1, 3, 4, 4, 4, 4, 2, 5]);