readme file modified

Author: tejas-2232

10. Caesar Cipher/CaesarCipher.js

@@ -0,0 +1,23 @@
+const allShifts = [...Array(26).keys()]
+const cipher = (str, keys=allShifts) => {
+ const chars = str.split("")
+ const res = keys.map( key => {
+ return chars.map( c => {
+ const char = c.charCodeAt(0)
+ if(char > 64 && char < 91)
+ {
+ return String.fromCharCode(65 + (char + key) % 65 % 26)
+ }
+ else if(char > 96 && char < 123)
+ {
+ return String.fromCharCode(97 + (char + key) % 97 % 26)
+ }
+ else
+ {
+ return String.fromCharCode(char)
+ }
+ })
+ })
+
+ return res.map( (r, i) => { return { key: keys[i], result: r.join("") } } )
+}

11. Lexicographically Equal Strings/lexicographically_equal_strings.js

@@ -0,0 +1,72 @@
+//LEXICOGRAPHICALLY EQUAL STRINGS CHALLENGE:
+
+/*
+Algorithm to find whether the two given strings in text format are lexicographically equal or not.
+
+A lexicographically equal strings are those strings which has the same length and contain the same characters in the same positions.
+
+*/
+//code Implementation
+// 1. chaining all the functions that are used.
+
+
+function check_lexicographic(str1,str2){
+
+ //Step-1: Convert the strings into the arrays of character using "split()" method.
+ let arr_str1=str1.split("");
+ let arr_str2=str2.split("");
+
+ //Step-2: Check whether the given strings has same lenght or not by calling "check_length()" function.
+ let len=check_length(str1,str2);
+
+ //Step-3: Check whether the given strings contain the same characters in the same positions or not by calling "check_positions()" function.
+ let positions=check_positions(arr_str1,arr_str2,len);
+ 
+ //Step-4: Return whether the strings are lexicographically equal or not.
+ return positions;
+}
+
+// 2. finding length of both the strings using lenght property and comparing them .
+function check_length(str1,str2){
+ //Finding lengths.
+ let len_str1=str1.length;
+ let len_str2=str2.length;
+
+ //Comapring lengths.
+ if (len_str1===len_str2){
+ return true;
+ }
+ else{
+ return false;
+ 
+ }
+}
+ 
+// 3. comparing positions of every characters in both the strings.
+function check_positions(arr_str1,arr_str2,len){
+ 
+ if(len===true){
+
+ let count=0;
+ //Using for loop.
+ for(let i=0;i<arr_str1.length;i++){
+ if (arr_str1[i]===arr_str2[i]){
+ count++;
+ }
+ }
+
+ //Checking whether the strings are lexicographically equal or not.
+ if (count===arr_str1.length){
+ return true;
+ }
+ else{
+ return false;
+ }
+ }
+ else{
+ return false;
+ }
+}
+
+//displaying result in the console
+console.log(check_lexicographic("javascript","javascript"));

README.md

@@ -703,6 +703,8 @@ It's that simple! Hope this helps.
 <hr>
 <hr>
 
+
+=======
 <b>8. Binary Search Tree </b> 
 Building, traversing or finding values in Binary Search Trees
 
@@ -971,13 +973,23 @@ It's very simple ones you realize it.
 <hr>
 <hr>
 
-<b>10. Name </b>
+<b>10. Caesar Cipher </b>
 
-__The challenge:__ <p> </p>
+__The challenge:__ <p> Given a string and a shift key, encrypt the string through Caesar Cipher.</p>
 
+__Algorithmic Thinking:__ <p> This is a very simple algorithm that requires only a tiny bit of prerequisite knowledge regarding ASCII, and also some discretion when processing possible over 26 keys. Basically we just need to know that all chracters are stored as numbers in computer memory according to the ASCII standard: https://www.w3schools.com/charsets/ref_html_ascii.asp. And that the modulus function is our friend :)</p>
 
-__Algorithmic Thinking:__ <p> </p>
 
+__code Implementation:__ <p>
+ 
+So first of all we need to split the string into characters to be processed individually and convert it to ASCII codes. Then we must check whether the character is either uppercase or lowercase(everything else should be kept the same) then add the key to it accordingly. But it is not a simple matter of simply doing ```char + key``` because for example, by shifting X by 3 we should get A. However, X(88) + 3 equals to 91 which is "\[". Thus what we should be doing is:
+ 
+```js
+// js has built in String.charCodeAt() method to help us get the ASCII code 
+// https://www.w3schools.com/jsref/jsref_charcodeat.asp
+// the reverse is String.fromCharCode()
+const char = charCodeAt("X")
+const key = 3
 
 __code Implementation:__ <p> </p>
 
@@ -995,3 +1007,4 @@ __Algorithmic Thinking:__ <p> </p>
 __code Implementation:__ <p> </p>
 <hr>
 <hr>
+