Algorithm in JavaScript to Merge Two Strings

Question

Hoping to learn better ways to solve this algorithm. The input consists of two strings.

Input - example 1:

var a = 'abc'
var b = 'def'

Expected Output

mergedString = 'adbecf';

My solution:

var a = 'abc';
var b = 'efg';

function mergeStr(a, b) {
  var aArr = a.split('');
  var bArr = b.split('');
  var newStr = '';

  for (var i = 0; i < aArr.length; i++) {
    newStr += aArr[i] + bArr[i];
  }
}

mergeStr(a, b);

The solution works for the input example above. But I was stuck when the second input values were given to me which is:

var a = 'ab';
var b = 'efg';

The expected output is:

aebfg

LOL since I was being timed I came up with the following junk. I just added an if statement to deal with the exact use case I was given. Obviously this solution is junk. I would really like to see what others would do.

function mergeStr(a, b) {
  var aArr = a.split('');
  var bArr = b.split('');
  var newStr = '';

  for (var i = 0; i < aArr.length; i++) {
    newStr += aArr[i] + bArr[i];
  }

  if (a.length < b.length) {
    newStr += b[2];
  }

  console.log(newStr);
}

Sirko · Accepted Answer · 2017-11-30 18:00:22Z

3

An alternative using somewhat fewer comparisons in contrast to the other (current) answers.

function mergeStr( str1, str2 ) {
  let merged = "";
  const min = Math.min( str1.length, str2.length );

  // first part: take from both strings
  for( let i=0; i<min; i++ ) {
    merged += str1[i] + str2[i];
  }

  // second part: take the rest from either string
  let largerStr= str1.length > str2.length ? str1 : str2;
  merged += largerStr.substr( min );

  return merged;
}

This takes the shorter length and basically uses your approach for the first few characters. Afterwards, it just appends the rest of the larger string.

answered Nov 30, 2017 at 18:00

Sirko

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2 Comments

davidbuzatto Over a year ago

Good approach like in merge/quick sort when the values does not need to be swapped anymore ;)

Aaron Balthaser Over a year ago

This is a nice function. Thanks.

davidbuzatto · Accepted Answer · 2017-11-30 17:58:53Z

1

You can access each string character like an array, you don't need to use split them to do this.

My solution uses the ternary operator:

function merge( str1, str2 ) {
    let merged = "";
    let max = str1.length > str2.length ? str1.length : str2.length;
    for ( let i = 0; i < max; i++ ) {
        merged += ( str1[i] ? str1[i] : "" ) + ( str2[i] ? str2[i] : "" );
    }
    return merged;
}

// prints acbd
console.log( merge( "ab", "cd") );

// str1 is bigger, prints acbdx
console.log( merge( "abx", "cd") );

// str1 is bigger, prints acbdxy
console.log( merge( "abxy", "cd") );

// str2 is bigger, prints acbdx
console.log( merge( "ab", "cdx") );

// str2 is bigger, prints acbdxy
console.log( merge( "ab", "cdxy") );

edited Nov 30, 2017 at 17:58

answered Nov 30, 2017 at 17:51

davidbuzatto

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1 Comment

Aaron Balthaser Over a year ago

Yeah thats a nice function. Scales with all the use cases I tested. Thanks.

rupps · Accepted Answer · 2017-12-01 00:07:41Z

1

I like one liners ..

function algo(str1,str2) {
    return Array.from(str1.length >= str2.length ? str1 : str2).map( (v,i) => (str1[i]||"")+(str2[i]||"") ).join("")
}

edited Dec 1, 2017 at 0:07

answered Nov 30, 2017 at 18:04

rupps

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2 Comments

Sirko Over a year ago

couldn't you use the index parameter of the map() callback instead of i?

rupps Over a year ago

trueeeeee hahaha

Naren Murali · Accepted Answer · 2017-11-30 18:07:10Z

0

How about finding the max length variable, then looping through it and if undefined fallback to a empty string.

var a = 'ab';
var b = 'efg';

function mergeStr(a, b) {
  let newStr = '';
  let len = Math.max(a.length - 1, b.length - 1);
  for (let i = 0; i <= len; i++) {
    newStr += (a[i] || "") + (b[i] || "");
  }
  return newStr;
}

console.log(mergeStr(a, b));

edited Nov 30, 2017 at 18:07

answered Nov 30, 2017 at 17:58

Naren Murali

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1 Comment

davidbuzatto Over a year ago

You don't need to split and use let instead of var ;)

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