Intermediate Algorithm Scripting

Sum All Numbers in a Range

將某範圍的數加總起來

freeCodeCamp Algorithm Challenge Guide: Sum All Numbers in a Range - Guide - freeCodeCamp Forum

我最一開始的想法

Math.max不吃矩陣，所以要加.apply
從陣列計算最大和最小值
javascript - How does the Math.max.apply() work? - Stack Overflow

function sumAll(arr) {
  var result=0;  

  min = Math.min.apply(null,arr);
  max = Math.max.apply(null,arr);

  for(i=min; i<=max; i++){
      result = result + i;
  }

  console.log(result);
  return result;
}

sumAll([1, 100]);

官方答案是用公式解 XD

function sumAll(arr) {
  max=Math.max(arr[0],arr[1]);
  min=Math.min(arr[0],arr[1]);
  return (max+min)*(max-min+1)/2;
}

Diff Two Arrays

抓出兩個陣列中，沒有重複的值

function diffArray(arr1, arr2) {
    var newArr = [];
    // Same, same; but different.

    // filter
    var newarr1 = arr1.filter(function(x){
        if(arr2.indexOf(x) === -1){
            return true;
        } else {
            return false;
        }
    });
    // console.log(newarr1)

    var newarr2 = arr2.filter(function(x){
        if(arr1.indexOf(x) === -1){
            return true;
        } else {
            return false;
        }
    });
    // console.log(newarr2)


    // concat
    newArr = newarr1.concat(newarr2);


    // Check
    console.log(newArr);
    return newArr;
  }

  diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);

有趣的解法

function diffArray(a, b){
 c = a.concat(b)
 d = [];
var diffarr = c.filter(function(c1){
       if (a.indexOf(c1) === -1 || b.indexOf(c1) === -1){
               d.push(c1);
       }
    });
    return d;
}
diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);

Roman Numeral Converter

阿拉伯數字轉羅馬數字覺得頭暈

function convertToRoman(num) {

    // var something
    var M, D, C, L, X, V, I;
    var Rarr = [M, D, C, L, X, V, I];
    var RSarr = ["M", "D", "C", "L", "X", "V", "I"];
    var Rarrnum = [1000, 500, 100, 50, 10, 5, 1];

    // get remainder array
    var Rresult = divide(num);
    console.log(Rresult);

    function divide(num) {
        var temp = num;

        for (i = 0; i < Rarr.length; i++) {
            Rarr[i] = Math.floor(temp / Rarrnum[i]);
            temp = temp % Rarrnum[i];
        }

        return Rarr;
    }


    // get roman number
    var end = join(Rresult);
    console.log(end);

    function join(Rresult) {
        var result = "";
        for (i = 0; i < Rresult.length; i = i + 2) {

            // ex: 9 = IX
            if (Rresult[i - 1] === 1 && Rresult[i] === 4) {
                result = result + RSarr[i] + RSarr[i - 2];
            }

            // ex: 4 = IV
            else if (Rresult[i - 1] === 0 && Rresult[i] === 4) {
                result = result + RSarr[i] + RSarr[i - 1];
            }

            // ex: 7 = VII
            else if (Rresult[i - 1] === 1) {
                result = result + RSarr[i - 1];
                for (j = 0; j < Rresult[i]; j++) {
                    result = result + RSarr[i];
                }
            }

            // ex: 2 = II
            else {
                for (j = 0; j < Rresult[i]; j++) {
                    result = result + RSarr[i];
                }
            }
        }
        return result;
    }
    return end;


}

convertToRoman(1004);

其他，先把4,9的組合列出來

function convert(num) {

    var Rarr = ["M", "CM","D", "CD", "C", "XC","L", "XL",  "X", "IX", "V", "IV", "I"];
    var Rarrnum = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
    var str = "";

    for(i=0; i<Rarr.length; i++){

        while(Rarrnum[i] <= num ){
            str = str + Rarr[i];
            num = num - Rarrnum[i];
        }

    }

    console.log(str);
    return str;

   }

   convert(3249);

Wherefore art thou

function whatIsInAName(collection, source) {
    // What's in a name?
    var arr = "";
    // Only change code below this line

    // source 的所有 key
    var keys2 = Object.keys(source);    

    for(i=0; i<collection.length; i++){
        for(j=0; j<keys2.length; j++){
            result = collection[i].hasOwnProperty(keys2[j]);

        }

    }
    a = keys2[0];



    // Only change code above this line
    console.log();
    return arr;
  }

  whatIsInAName([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" });

今天的成果

function whatIsInAName(collection, source) {
    // What's in a name?
    var arr = [];
    // Only change code below this line


    // source 的所有 key
    var keys2 = Object.keys(source);
    console.log(keys2.length);

    var fitCount = [];


    for(i=0; i<collection.length; i++){

        fitCount[i] = 0;

        // 紀錄 collection[i] 中有多少與 source 相同的 key value 對 
        for (var Skey in source){
            if(collection[i].hasOwnProperty(Skey) && collection[i][Skey]===source[Skey]){
                console.log("i="+i+", key="+Skey+", value="+collection[i][Skey]);
                fitCount[i] = fitCount[i] + 1; 
            }
        }

        // 如果 fitCount[i] 與 source 的長度相同，就把 fitCount[i] 放進 arr
        if(fitCount[i] == keys2.length){
            arr.push(collection[i]);
        }
    }

    // Only change code above this line
    console.log(arr);
    return arr;
  }

  whatIsInAName([{ "a": 1, "b": 2 }, { "a": 1 }, { "a": 1, "b": 2, "c": 2 }], { "a": 1, "c": 2 });

用 filter 實做

function where(collection, source) {
    var arr = [];
    // What's in a name?

    arr = collection.filter(function(obj){

        var fitCount = 0;
        for (var key in source){
            if(obj[key] == source[key]){
                fitCount += 1;
            }
        }

        return fitCount == Object.keys(source).length;

    });

    console.log(arr);
    return arr;
  }

  where([{ "a": 1, "b": 2 }, { "a": 1 }, { "a": 1, "b": 2, "c": 2 }], { "a": 1, "c": 2 });

節錄一個詭異的解法 (很多解法我都摸不著頭緒)

function whatIsInAName(collection, source) {
  // What's in a name?  
  return collection
    .filter((obj) => JSON.stringify(Object.assign(JSON.parse(JSON.stringify(obj)), source)) === JSON.stringify(obj));
}

Search and Replace

用 after 取代 before，但首字大小寫要相同

function myReplace(str, before, after) {

    // If "before" first alphabet is Upper
    var isUpper = /[A-Z]/.test(before[0]);
    console.log(isUpper);

    // If "before" first alphabet is Upper, then change after first alphabet to Upper
    if ( isUpper ){
        var afterArr = after.split("");
        afterArr[0] = afterArr[0].toUpperCase();
        after = afterArr.join("");
    }

    // Use "after" replace "before"
    str = str.replace(before, after);

    console.log(str);
    return str;
  }

  myReplace("He is Sleeping on the couch", "Sleeping", "sitting");

簡化了幾個部份

function myReplace(str, before, after) {

    // If "before" first alphabet is Upper
    var isUpper = /[A-Z]/.test(before[0]);
    console.log(isUpper);

    // If "before" first alphabet is Upper, then change after first alphabet to Upper
    if ( isUpper ){
        after = after[0].toUpperCase() + after.slice(1);
    }

    // Use "after" replace "before"
    str = str.replace(new RegExp(before, "g"), after);

    console.log(str);
    return str;
  }

  myReplace("He is Sleeping on the Sleeping couch", "Sleeping", "sitting")

Pig Latin

freeCodeCamp Algorithm Challenge Guide: Pig Latin - Guide - freeCodeCamp Forum

我的解法

function translatePigLatin(str) {

    var isVowel = /^[aeiou]/.test(str);
    var newStr;

    if (isVowel) {
        //+way
        newStr = str + "way";
    } else {
        // first consonant + ay

        var muYin = ["a", "e", "i", "o", "u"];
        var muYinIndex = new Array(str.length);

        muYinIndex = muYin.map(function(item) {
            return str.indexOf(item);
        });

        minIndexArray = muYinIndex.filter(function(item) {
            return item > -1
        });

        minIndex = Math.min.apply(Math, minIndexArray);

        newStr = str.slice(minIndex) + str.slice(0, minIndex) + "ay";
    }

    console.log(newStr);
    return newStr;
}

translatePigLatin("glove");

依照我的流程，可以化約為這個語法

function translatePigLatin(str) {
  var vowel = /[(a/e/i/o/u)]/igm;
  var consonant = /[^(a/e/i/o/u)]/igm;
  var v =  str.search(vowel);
  var c =  str.search(consonant);
    return v > c ?  str.slice(v) + str.substr(c, v) + "ay" : str + "way";
}

完全用 replace

function translatePigLatin(str) {
  return str
    .replace(/^([aeiouy])(.*)/, '$1$2way')
    .replace(/^([^aeiouy]+)(.*)/, '$2$1ay');
}

// test here
translatePigLatin("consonant");

DNA Pairing

freeCodeCamp Algorithm Challenge Guide: DNA Pairing - Guide - freeCodeCamp Forum

我的解法

function pairElement(str) {

    var arr = str.split("");
    var newArr = [];

    function switchATCH(ATCG){
        switch( ATCG ){
            case "A":
                newArr.push(["A", "T"]);
                break;
            case "T":
                newArr.push(["T", "A"]);
                break;
            case "C":
                newArr.push(["C", "G"]);
                break;
            case "G":
                newArr.push(["G","C"]);
                break;    
        }
    }

    arr.map(function(item){
        switchATCH(item);
    });


    console.log(newArr);
    return newArr;
  }

  pairElement("ATCG");

討論區的一個解法

function pairElement(str) {
  var pairs = {
    "A": ["A", "T"],
    "T": ["T", "A"],
    "C": ["C", "G"],
    "G": ["G", "C"]
  };

  return str.split("").map(function(elem) {
    return pairs[elem];
  });

別人更簡短的版本

function pairElement(str) {  
  return str.split("").map(function (x) {
    switch (x) {
      case "G":
       return ["G","C"];       
      case "C":   
       return ["C","G"];        
      case "T":
       return ["T","A"];       
      case "A":
       return ["A","T"];       
    }    
  });
}

之後的解法

function pair(str) {

    var obj = {
        "A": ["A", "T"],
        "T": ["T", "A"],
        "C": ["C", "G"],
        "G": ["G", "C"]
    }

    var newArr = str.split("").map(function(key){
        return obj[key];
    });

    console.log(newArr);
    return newArr;
  }

  pair("GCG");

Missing letters

freeCodeCamp Algorithm Challenge Guide: Missing Letters - Guide - freeCodeCamp Forum

自己想的

function fearNotLetter(str) {
  var char;
  var charNum;

  for (i = 0; i < str.split("").length; i++) {
    if (str.charCodeAt(i) - str.charCodeAt(i - 1) == 2) {
      charNum = str.charCodeAt(i) - 1;
      char = String.fromCharCode(charNum);
    }
  }

  console.log(char);
  return char;
}

fearNotLetter("abce"); // d

可以抓出所有缺少的字

function fearNotLetter(str) {
  var allChars = '';
  var notChars = new RegExp('[^'+str+']','g');

  for (var i = 0; allChars[allChars.length-1] !== str[str.length-1] ; i++)
    allChars += String.fromCharCode(str[0].charCodeAt(0) + i);

  return allChars.match(notChars) ? allChars.match(notChars).join('') : undefined;
}

// test here
fearNotLetter("abce");

Boo who

freeCodeCamp Algorithm Challenge Guide: Boo Who - Guide - freeCodeCamp Forum

自己想的

function booWho(bool) {
  // What is the new fad diet for ghost developers? The Boolean.

  if(bool===true || bool===false){
    return true;
  } else{
    return false;
  }

}

booWho(null);

解答

function booWho(bool) {
  return typeof bool === 'boolean';
}

// test here
booWho(null);

Sorted Union

freeCodeCamp Algorithm Challenge Guide: Sorted Union - Guide - freeCodeCamp Forum

自己想的

function uniteUnique(arr) {

  var newArr = arguments[0];

  for(i=1; i<arguments.length; i++){
    for(j=0; j<arguments[i].length; j++){
      var numIndex = arguments[0].indexOf(arguments[i][j]);
      if(numIndex<0){
        newArr.push(arguments[i][j]);
      }
    }
  }

  console.log(newArr);
  return newArr;
}

uniteUnique([1, 2, 3], [5, 2, 1, 4], [2, 1], [6, 7, 8]);

ES6新的函式，有點像集合的概念，在 set 中重複的值會被刪除

Set - JavaScript | MDN

//jshint esversion:6

function uniteUnique(arr) {

  //make an array out of arguments and flatten it (using the spread operator)
  const args = [].concat(...arguments);

  // create a Set
  return [...new Set(args)];
}

// test here
uniteUnique([1, 3, 2], [5, 2, 1, 4], [2, 1]);

Convert HTML Entities

freeCodeCamp Algorithm Challenge Guide: Convert HTML Entities - Guide - freeCodeCamp Forum

自己想的

function convertHTML(str) {
  // &colon;&rpar;

  var newStr = str;
  var obj = {
    "&": "&amp;",
    "<": "&lt;",
    ">": "&gt;",
    '"': "&quot;",
    "'": "&apos;"
  };

  for ( var key in obj){
    newStr = newStr.replace(new RegExp(key, "g"), obj[key]);    
  }

  console.log(newStr);
  return newStr;
}

convertHTML("Hamburgers < Pizza < Tacos");

答案一

function convertHTML(str) {
  // Use Object Lookup to declare as many HTML entities as needed.
  var htmlEntities = {
    '&':'&amp;',
    '<':'&lt;',
    '>':'&gt;',
    '\"':'&quot;',
    '\'':"&apos;"
  };
  //Use map function to return a filtered str with all entities changed automatically.
  return str.split('').map(function(entity){
    return htmlEntities[entity] || entity;
  }).join('');
}

// test here
convertHTML("Dolce & Gabbana");

答案二

function convertHTML(str) {

 function repEnt(ent){
  switch(ent){
    case "&":
      return "&amp;";
    case "<":
      return "&lt;"; 
    case ">":
      return "&gt;";
    case '"':
      return '&quot;';
    case "'":
      return "&apos;";  
    }
 }
  str = str.replace( /[&<>"']/g, repEnt ); 
  return str;
}

convertHTML("Dolce & Gabbana");

答案三

function convertHTML(str) {
  var entities = { '&': '&amp;', '<':'&lt;', '>': '&gt;', '"': '&quot;', "'": '&apos;'}
  return str.replace(/[&<>"']/g, function(match) {
    return entities[match]
  } )
}

Spinal Tap Case

function spinalCase(str) {
  // "It's such a fine line between stupid, and clever."
  // --David St. Hubbins

  var newStr;

  newStr = str.match(/[A-Z][a-z]*/g);
  // newStr = newStr.replace(/[_-\s]/gi, "-");


  console.log(newStr);
  return newStr;
}

spinalCase('Teletubbies say Eh-oh');

PreviousIntermediate Front End Development Projects

Last updated 5 years ago

hashtagSum All Numbers in a Range

hashtagDiff Two Arrays

hashtagRoman Numeral Converter

hashtagWherefore art thou

hashtagSearch and Replace

hashtagPig Latin

hashtagDNA Pairing

hashtagMissing letters

hashtagBoo who

hashtagSorted Union

hashtagConvert HTML Entities

hashtagSpinal Tap Case

Sum All Numbers in a Range

Diff Two Arrays

Roman Numeral Converter

Wherefore art thou

Search and Replace

Pig Latin

DNA Pairing

Missing letters

Boo who

Sorted Union

Convert HTML Entities

Spinal Tap Case