Hướng dẫn caesars cipher - javascript freecodecamp - caesars cipher - javascript freecodecamp
Dung dịchOffical soln: var lookup = { 'A': 'N','B': 'O','C': 'P','D': 'Q', 'E': 'R','F': 'S','G': 'T','H': 'U', 'I': 'V','J': 'W','K': 'X','L': 'Y', 'M': 'Z','N': 'A','O': 'B','P': 'C', 'Q': 'D','R': 'E','S': 'F','T': 'G', 'U': 'H','V': 'I','W': 'J','X': 'K', 'Y': 'L','Z': 'M' }; function rot13(encodedStr) { var codeArr = encodedStr.split(""); // String to Array var decodedArr = []; // Your Result goes here // Only change code below this line decodedArr = codeArr.map(function(letter) { if(lookup.hasOwnProperty(letter)) { letter = lookup[letter]; } return letter; }); // Only change code above this line return decodedArr.join(""); // Array to String } Soln của tôi: function rot13(str) { // LBH QVQ VG! const Acode='A'.charCodeAt(); const Ncode='N'.charCodeAt(); const Zcode='Z'.charCodeAt(); return [...str].map( function(e){ const code=e.charCodeAt(); if(Acode<=code && code<=Zcode){ if(code<Ncode){ return String.fromCharCode(code+13); } else { return String.fromCharCode(code-13); } } else { return e; } } ).join(""); } // Change the inputs below to test rot13("SERR PBQR PNZC"); Hướng dẫn thử thách Freecodecamp: Caesars Code: Soln 2: // Solution with Regular expression and Array of ASCII character codes function rot13(str) { var rotCharArray = []; var regEx = /[A-Z]/; str = str.split(""); for (var x in str) { if (regEx.test(str[x])) { // A more general approach // possible because of modular arithmetic // and cyclic nature of rot13 transform rotCharArray.push(((str[x].charCodeAt() - 65 + 13) % 26) + 65); } else { rotCharArray.push(str[x].charCodeAt()); } } str = String.fromCharCode.apply(String, rotCharArray); return str; } Algorithm Explanation: ALPHA KEY BASE ROTATED ROT13 ------------------------------------------------------------- [A] 65 <=> 0 + 13 => 13 % 26 <=> 13 + 65 = 78 [N] [B] 66 <=> 1 + 13 => 14 % 26 <=> 14 + 65 = 79 [O] [C] 67 <=> 2 + 13 => 15 % 26 <=> 15 + 65 = 80 [P] [D] 68 <=> 3 + 13 => 16 % 26 <=> 16 + 65 = 81 [Q] [E] 69 <=> 4 + 13 => 17 % 26 <=> 17 + 65 = 82 [R] [F] 70 <=> 5 + 13 => 18 % 26 <=> 18 + 65 = 83 [S] [G] 71 <=> 6 + 13 => 19 % 26 <=> 19 + 65 = 84 [T] [H] 72 <=> 7 + 13 => 20 % 26 <=> 20 + 65 = 85 [U] [I] 73 <=> 8 + 13 => 21 % 26 <=> 21 + 65 = 86 [V] [J] 74 <=> 9 + 13 => 22 % 26 <=> 22 + 65 = 87 [W] [K] 75 <=> 10 + 13 => 23 % 26 <=> 23 + 65 = 88 [X] [L] 76 <=> 11 + 13 => 24 % 26 <=> 24 + 65 = 89 [Y] [M] 77 <=> 12 + 13 => 25 % 26 <=> 25 + 65 = 90 [Z] [N] 78 <=> 13 + 13 => 26 % 26 <=> 0 + 65 = 65 [A] [O] 79 <=> 14 + 13 => 27 % 26 <=> 1 + 65 = 66 [B] [P] 80 <=> 15 + 13 => 28 % 26 <=> 2 + 65 = 67 [C] [Q] 81 <=> 16 + 13 => 29 % 26 <=> 3 + 65 = 68 [D] [R] 82 <=> 17 + 13 => 30 % 26 <=> 4 + 65 = 69 [E] [S] 83 <=> 18 + 13 => 31 % 26 <=> 5 + 65 = 70 [F] [T] 84 <=> 19 + 13 => 32 % 26 <=> 6 + 65 = 71 [G] [U] 85 <=> 20 + 13 => 33 % 26 <=> 7 + 65 = 72 [H] [V] 86 <=> 21 + 13 => 34 % 26 <=> 8 + 65 = 73 [I] [W] 87 <=> 22 + 13 => 35 % 26 <=> 9 + 65 = 74 [J] [X] 88 <=> 23 + 13 => 36 % 26 <=> 10 + 65 = 75 [K] [Y] 89 <=> 24 + 13 => 37 % 26 <=> 11 + 65 = 76 [L] [Z] 90 <=> 25 + 13 => 38 % 26 <=> 12 + 65 = 77 [M] Soln 3: function rot13(str) { // LBH QVQ VG! return str.replace(/[A-Z]/g, L => String.fromCharCode((L.charCodeAt(0) % 26) + 65) ); } As you can notice, each number in the range of [65 - 90] maps to a unique number between [0 - 25]. You might have also noticed that each given number (e.g. 65) maps to another number (e.g. 13) which can be used as an offset value (i.e. 65 + OFFSET) to get the ROT13 of the given number. E.g. 65 maps to 13 which can be taken as an offset value and added to 65 to give 78. [A] 65 % 26 ⇔ 13 + 65 = 78 [N] [B] 66 % 26 ⇔ 14 + 65 = 79 [O] [C] 67 % 26 ⇔ 15 + 65 = 80 [P] [D] 68 % 26 ⇔ 16 + 65 = 81 [Q] [E] 69 % 26 ⇔ 17 + 65 = 82 [R] [F] 70 % 26 ⇔ 18 + 65 = 83 [S] [G] 71 % 26 ⇔ 19 + 65 = 84 [T] [H] 72 % 26 ⇔ 20 + 65 = 85 [U] [I] 73 % 26 ⇔ 21 + 65 = 86 [V] [J] 74 % 26 ⇔ 22 + 65 = 87 [W] [K] 75 % 26 ⇔ 23 + 65 = 88 [X] [L] 76 % 26 ⇔ 24 + 65 = 89 [Y] [M] 77 % 26 ⇔ 25 + 65 = 90 [Z] [N] 78 % 26 ⇔ 0 + 65 = 65 [A] [O] 79 % 26 ⇔ 1 + 65 = 66 [B] [P] 80 % 26 ⇔ 2 + 65 = 67 [C] [Q] 81 % 26 ⇔ 3 + 65 = 68 [D] [R] 82 % 26 ⇔ 4 + 65 = 69 [E] [S] 83 % 26 ⇔ 5 + 65 = 70 [F] [T] 84 % 26 ⇔ 6 + 65 = 71 [G] [U] 85 % 26 ⇔ 7 + 65 = 72 [H] [V] 86 % 26 ⇔ 8 + 65 = 73 [I] [W] 87 % 26 ⇔ 9 + 65 = 74 [J] [X] 88 % 26 ⇔ 10 + 65 = 75 [K] [Y] 89 % 26 ⇔ 11 + 65 = 76 [L] [Z] 90 % 26 ⇔ 12 + 65 = 77 [M] Soln 4: function rot13(str) { const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; return str .split('') .map(char => { const pos = alphabet.indexOf(char); return pos >= 0 ? alphabet[(pos + 13) % 26] : char; }) .join(''); } |