我知道过去曾有一些有关Caesar Ciphers的帖子,我曾浏览过,但我没有找到能帮助我解决此问题的答案,因此是我的帖子。
语言是JavaScript。我已经编写了3个测试,到目前为止,其中2个通过了测试,但第三个测试没有通过。我尝试使用嵌套的for循环遍历字母和str,并进行比较,然后根据数字进行上下移动字母索引,然后将该字母推入新数组,然后返回连接的数组最后。
它适用于正数,但不适用于负数。 (我还应该指出,我还没有想到如何处理空格,我只是想先让它适用于单个单词,然后再从那里获取,谢谢!)
任何朝着正确方向的指针都会受到赞赏。
卡塔说明:
函数caesarCipher应该采用一个字符串和一个数字(n),并返回一个应用了Caesar密码的新字符串。凯撒密码将每个明文字母替换为一个不同的字母,在字母的上方或下方固定数量的位置。 N表示应应用字母的上移或下移次数。可能是负面的也可能是正面的。
E.g.
caesarCipher('hello', 2)
--> 'jgnnq'
caesarCipher('hello world!', -3)
--> 'ebiil tloia!'
我的测试:
const caesarCipher = require("../katas/caesar-cipher");
const { expect } = require("chai");
describe.only("caesarCipher", () => {
it("returns an empty string when passed an empty string", () => {
const alphabet = [
"a",
"b",
"c",
"d",
"e",
"f",
"g",
"h",
"i",
"j",
"k",
"l",
"m",
"n",
"o",
"p",
"q",
"r",
"s",
"t",
"u",
"v",
"w",
"x",
"y",
"z"
];
const str = "";
const num = 2;
const actualResults = caesarCipher(alphabet, str, num);
const expectedResults = "";
expect(actualResults).to.equal(expectedResults);
});
it("returns a string with the letters replaced by the number of shifts up the alphabet", () => {
const alphabet = [
"a",
"b",
"c",
"d",
"e",
"f",
"g",
"h",
"i",
"j",
"k",
"l",
"m",
"n",
"o",
"p",
"q",
"r",
"s",
"t",
"u",
"v",
"w",
"x",
"y",
"z"
];
const str = "hi";
const num = 2;
const actualResults = caesarCipher(alphabet, str, num);
const expectedResults = "jk";
expect(actualResults).to.equal(expectedResults);
});
it("returns a string with the letters replaced by the number of shifts down the alphabet", () => {
const alphabet = [
"a",
"b",
"c",
"d",
"e",
"f",
"g",
"h",
"i",
"j",
"k",
"l",
"m",
"n",
"o",
"p",
"q",
"r",
"s",
"t",
"u",
"v",
"w",
"x",
"y",
"z"
];
const str = "dog";
const num = -3;
const actualResults = caesarCipher(alphabet, str, num);
const expectedResults = "ald";
expect(actualResults).to.equal(expectedResults);
});
});
我的解决方案:
function caesarCipher(alphabet, str, num) {
const strToArray = str.split("");
console.log(strToArray);
const cipheredStr = [];
for (let i = 0; i < strToArray.length; i++) {
for (let j = 0; j < alphabet.length; j++) {
if (strToArray[i] === alphabet[j] && Math.sign(num) === 1) {
console.log(Math.sign(num));
cipheredStr.push(alphabet[(j += num)]);
} else if (strToArray[i] === alphabet[j] && Math.sign(num) === -1) {
console.log(Math.sign(num));
console.log(alphabet[(j -= num)]);
cipheredStr.push(alphabet[(j -= num)]);
}
}
}
console.log(cipheredStr.join(""));
return cipheredStr.join("");
}
结果:
caesarCipher
[]
✓ returns an empty string when passed an empty string
[ 'h', 'i' ]
1
1
jk
✓ returns a string with the letters replaced by the number of shifts up the alphabet
[ 'd', 'o', 'g' ]
-1
g
-1
r
-1
j
jum
1) returns a string with the letters replaced by the number of shifts down the alphabet
2 passing (15ms)
1 failing
1) caesarCipher
returns a string with the letters replaced by the number of shifts down the alphabet:
AssertionError: expected 'jum' to equal 'ald'
+ expected - actual
-jum
+ald
at Context.<anonymous> (spec/caesar-cipher.spec.js:108:30)
at processImmediate (internal/timers.js:456:21)
答案 0 :(得分:1)
问题是当tableb
为负数时,您正在执行映射:
num
但是cipheredStr.push(alphabet[(j -= num)]);
是负数。当您减去负数时,您正在做的就是加上它的绝对值。
相反,您应该这样做:
num
另外,请注意,要计算字母表中的索引,无需在其中放置cipheredStr.push(alphabet[j + num]);
。
我了解您的解决方案仍在进行中。您必须考虑:
=
求和以进行翻译并且超出字母范围时,会发生什么情况。负值j + num
可能会发生同样的事情。num
仅应接受两个参数,但是您将字母作为第一个参数传递!祝您的代码好运,并继续尝试:)