Showing unique characters in a string only once

问题

I have a string with repeated letters. I want letters that are repeated more than once to show only once. For instance I have a string aaabbbccc i want the result to be abc. so far my function works like this:

if the letter doesn't repeat, it's not shown
if it's repeated once, it's show only once (i.e. aa shows a)
if it's repeated twice, shows all (i.e. aaa shows aaa)
if it's repeated 3 times, it shows 6 (if aaaa it shows aaaaaa)

function unique_char(string) {
    var unique = '';
    var count = 0;
    for (var i = 0; i < string.length; i++) {
        for (var j = i+1; j < string.length; j++) {
            if (string[i] == string[j]) {
                count++;
                unique += string[i];
            }
        }
    }
    return unique;
}

document.write(unique_char('aaabbbccc'));

The function must be with loop inside a loop; that's why the second for is inside the first.

回答1:

Convert it to an array first, then use the answer here, and rejoin, like so:

var nonUnique = "ababdefegg";
var unique = nonUnique.split('').filter(function(item, i, ar){ return ar.indexOf(item) === i; }).join('');

All in one line :-)

回答2:

Fill a Set with the characters and concatenate its unique entries:

function makeUnique(str) {
  return String.prototype.concat(...new Set(str))
}

console.log(makeUnique('abc'));    // "abc"
console.log(makeUnique('abcabc')); // "abc"

回答3:

Too late may be but still my version of answer to this post:

function extractUniqCharacters(str){
    var temp = {};
    for(var oindex=0;oindex<str.length;oindex++){
        temp[str.charAt(oindex)] = 0; //Assign any value
    }
    return Object.keys(temp).join("");
}

回答4:

You can use a regular expression with a custom replacement function:

function unique_char(string) {
    return string.replace(/(.)\1*/g, function(sequence, char) {
         if (sequence.length == 1) // if the letter doesn't repeat
             return ""; // its not shown
         if (sequence.length == 2) // if its repeated once
             return char; // its show only once (if aa shows a)
         if (sequence.length == 3) // if its repeated twice
             return sequence; // shows all(if aaa shows aaa)
         if (sequence.length == 4) // if its repeated 3 times
             return Array(7).join(char); // it shows 6( if aaaa shows aaaaaa)
         // else ???
         return sequence;
    });
}

回答5:

Per the actual question: "if the letter doesn't repeat its not shown"

function unique_char(str)
{
    var obj = new Object();

    for (var i = 0; i < str.length; i++)
    {
        var chr = str[i];
        if (chr in obj)
        {
            obj[chr] += 1;
        }
        else
        {
            obj[chr] = 1;
        }
    }

    var multiples = [];
    for (key in obj)
    {
        // Remove this test if you just want unique chars
        // But still keep the multiples.push(key)
        if (obj[key] > 1)
        {
            multiples.push(key);
        }
    }

    return multiples.join("");
}

var str = "aaabbbccc";
document.write(unique_char(str));

回答6:

Your problem is that you are adding to unique every time you find the character in string. Really you should probably do something like this (since you specified the answer must be a nested for loop):

function unique_char(string){

    var str_length=string.length;
    var unique='';

    for(var i=0; i<str_length; i++){

        var foundIt = false;
        for(var j=0; j<unique.length; j++){

            if(string[i]==unique[j]){

                foundIt = true;
                break;
            }

        }

        if(!foundIt){
            unique+=string[i];
        }

    }

   return unique;
}

document.write( unique_char('aaabbbccc'))

In this we only add the character found in string to unique if it isn't already there. This is really not an efficient way to do this at all ... but based on your requirements it should work.

I can't run this since I don't have anything handy to run JavaScript in ... but the theory in this method should work.

回答7:

Using lodash:

_.uniq('aaabbbccc').join(''); // gives 'abc'

回答8:

Try this if duplicate characters have to be displayed once, i.e., for i/p: aaabbbccc o/p: abc

var str="aaabbbccc";
Array.prototype.map.call(str, 
  (obj,i)=>{
    if(str.indexOf(obj,i+1)==-1 ){
     return obj;
    }
  }
).join("");
//output: "abc"

And try this if only unique characters(String Bombarding Algo) have to be displayed, add another "and" condition to remove the characters which came more than once and display only unique characters, i.e., for i/p: aabbbkaha o/p: kh

var str="aabbbkaha";
Array.prototype.map.call(str, 
 (obj,i)=>{
   if(str.indexOf(obj,i+1)==-1 && str.lastIndexOf(obj,i-1)==-1){ // another and condition
     return obj;
   }
 }
).join("");
//output: "kh"

回答9:

<script>
    uniqueString = "";

    alert("Displays the number of a specific character in user entered string and then finds the number of unique characters:");

    function countChar(testString, lookFor) {
        var charCounter = 0;
        document.write("Looking at this string:<br>");

        for (pos = 0; pos < testString.length; pos++) {
            if (testString.charAt(pos) == lookFor) {
                charCounter += 1;
                document.write("<B>" + lookFor + "</B>");
            } else
                document.write(testString.charAt(pos));
        }
        document.write("<br><br>");
        return charCounter;
    }

    function findNumberOfUniqueChar(testString) {
        var numChar = 0,
            uniqueChar = 0;
        for (pos = 0; pos < testString.length; pos++) {
            var newLookFor = "";
            for (pos2 = 0; pos2 <= pos; pos2++) {
                if (testString.charAt(pos) == testString.charAt(pos2)) {
                    numChar += 1;
                }
            }
            if (numChar == 1) {
                uniqueChar += 1;
                uniqueString = uniqueString + " " + testString.charAt(pos)
            }
            numChar = 0;
        }
        return uniqueChar;
    }

    var testString = prompt("Give me a string of characters to check", "");
    var lookFor = "startvalue";
    while (lookFor.length > 1) {
        if (lookFor != "startvalue")
            alert("Please select only one character");
        lookFor = prompt(testString + "\n\nWhat should character should I look for?", "");
    }
    document.write("I found " + countChar(testString, lookFor) + " of the<b> " + lookFor + "</B> character");
    document.write("<br><br>I counted the following " + findNumberOfUniqueChar(testString) + " unique character(s):");
    document.write("<br>" + uniqueString)
</script>

回答10:

Here is the simplest function to do that

  function remove(text) 
    {
      var unique= "";
      for(var i = 0; i < text.length; i++)
      {
        if(unique.indexOf(text.charAt(i)) < 0) 
        {
          unique += text.charAt(i);
        }
      }
      return unique;
    }

来源：https://stackoverflow.com/questions/13868043/showing-unique-characters-in-a-string-only-once

标签

javascript

string

character

unique