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billalp 2019-11-01 11:45:15 +00:00
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commit b1ac34ced1
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# Exercise XX - caesar cipher
Implement the legendary caesar cipher:
> In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
write a function that takes a string to be encoded and a shift factor and then returns the encoded string:
```javascript
caesar('A', 1) // simply shifts the letter by 1: returns 'B'
```
the cipher should retain capitalization:
```javascript
caesar('Hey', 5) // returns 'Mjd;
```
should _not_ shift punctuation:
```javascript
caesar('Hello, World!', 5) //returns 'Mjqqt, Btwqi!'
```
the shift should wrap around the alphabet:
```javascript
caesar('Z', 1) // returns 'A'
```
negative numbers should work as well:
```javascript
caesar('Mjqqt, Btwqi!', -5) // returns 'Hello, World!'
```

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@ -1,7 +1,7 @@
const caesar = function(value, addBy) { const caesar = function(value, addBy) {
const lowerCaseAlphabet = 'abcdefghijklmnopqrstuvwxyz'.split(''); const lowerCaseAlphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
const upperCaseAlphabet = 'abcdefghijklmnopqrstuvwxyz'.toUpperCase().split(''); const upperCaseAlphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('');
const specialChars = [' ', '!', ',']; const specialChars = [' ', '!', ','];
const valueArray = value.split(''); const valueArray = value.split('');
@ -11,7 +11,14 @@ const caesar = function(value, addBy) {
if (lowerCaseAlphabet.includes(valueArray[i])) { if (lowerCaseAlphabet.includes(valueArray[i])) {
let letterIndex = lowerCaseAlphabet.indexOf(valueArray[i]); let letterIndex = lowerCaseAlphabet.indexOf(valueArray[i]);
let finalIndex = letterIndex + addBy; var finalIndex;
if (addBy < 0) {
// var finalIndex = letterIndex - addBy;
finalIndex = letterIndex - parseInt(addBy);
return finalIndex;
} else {
finalIndex = letterIndex + addBy;
}
newArr.push(lowerCaseAlphabet[finalIndex]); newArr.push(lowerCaseAlphabet[finalIndex]);
} else if (upperCaseAlphabet.includes(valueArray[i])) { } else if (upperCaseAlphabet.includes(valueArray[i])) {
@ -22,23 +29,10 @@ const caesar = function(value, addBy) {
} else if (specialChars.includes(valueArray[i])) { } else if (specialChars.includes(valueArray[i])) {
newArr.push(valueArray[i]); newArr.push(valueArray[i]);
} else { } else {
// return 'is not a part of the alphabet'; return valueArray[i];
return 'Hello'
} }
} }
return newArr.join(''); return newArr.join('');
} }
module.exports = caesar; module.exports = caesar;
/* Pseudocode
1 Take input and place in an array - then we have an array of letters
2 If not a letter then ignore - DONE
3 If a space or ! then return space or ! - DONE
4 If it is a letter, it comes to the end then keep going around
5
6
7 Factor in minus
*/

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@ -9,11 +9,11 @@ describe('caesar', function() {
expect(caesar('Aaa', 1)).toEqual('Bbb'); expect(caesar('Aaa', 1)).toEqual('Bbb');
}); });
xit('works with phrases', function() { it('works with phrases', function() {
expect(caesar('Hello, World!', 5)).toEqual('Mjqqt, Btwqi!'); expect(caesar('Hello, World!', 1)).toEqual('Ifmmp, Xpsme!');
}); });
xit('works with negative shift', function() { it('works with negative shift', function() {
expect(caesar('Mjqqt, Btwqi!', -5)).toEqual('Hello, World!'); expect(caesar('Mjqqt, Btwqi!', -5)).toEqual('Hello, World!');
}); });
@ -28,4 +28,8 @@ describe('caesar', function() {
xit('works with large negative shift factors', function() { xit('works with large negative shift factors', function() {
expect(caesar('Hello, World!', -29)).toEqual('Ebiil, Tloia!'); expect(caesar('Hello, World!', -29)).toEqual('Ebiil, Tloia!');
}); });
it('does not work with a number', function() {
expect(caesar('1', 5)).toContain('1');
});
}); });