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June 16, 2018 15:11
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freeCodeCamp JavaScript Algorithms and Data Structures Projects: Caesars Cipher
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// One of the simplest and most widely known ciphers is a Caesar cipher, | |
// also known as a shift cipher. In a shift cipher the meanings of the | |
// letters are shifted by some set amount. | |
// A common modern use is the ROT13 cipher, where the values of the | |
// letters are shifted by 13 places. Thus 'A' ↔ 'N', 'B' ↔ 'O' and so on. | |
// Write a function which takes a ROT13 encoded string as input and | |
// returns a decoded string. | |
// All letters will be uppercase. Do not transform any non-alphabetic | |
// character (i.e. spaces, punctuation), but do pass them on. | |
function rot13(str) { // LBH QVQ VG! | |
let maxAscii=90; | |
let minAscii=65; | |
let rotate=13; | |
return str.split('').map(letter => { | |
let curLetter=letter.charCodeAt(); | |
if ((curLetter >= minAscii) && (curLetter <= maxAscii)) { | |
curLetter-=13; | |
if (curLetter<65) { curLetter+=26; } | |
} | |
return String.fromCharCode(curLetter);}).join(""); | |
} | |
// Change the inputs below to test | |
rot13("SERR PBQR PNZC"); // FREE CODE CAMP | |
rot13("SERR CVMMN!"); // FREE PIZZA! | |
rot13("SERR YBIR?"); // FREE LOVE? | |
rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT."); // THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG. |
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