number-of-balanced-integers-in-a-range

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Algorithms

You are given two integers <code>low</code> and <code>high</code>.

An integer is called balanced if it satisfies both of the following conditions:

<ul>
	<li>It contains at least two digits.</li>
	<li>The sum of digits at even positions is equal to the sum of digits at odd positions (the leftmost digit has position 1).</li>
</ul>

Return an integer representing the number of balanced integers in the range <code>[low, high]</code> (both inclusive).

&nbsp;
Example 1:

<div class="example-block">
Input: low = 1, high = 100

Output: 9

Explanation:

The 9 balanced numbers between 1 and 100 are 11, 22, 33, 44, 55, 66, 77, 88, and 99.
</div>

Example 2:

<div class="example-block">
Input: low = 120, high = 129

Output: 1

Explanation:

Only 121 is balanced because the sum of digits at even and odd positions are both 2.
</div>

Example 3:

<div class="example-block">
Input: low = 1234, high = 1234

Output: 0

Explanation:

1234 is not balanced because the sum of digits at odd positions <code>(1 + 3 = 4)</code> does not equal the sum at even positions <code>(2 + 4 = 6)</code>.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= low &lt;= high &lt;= 1015</code></li>
</ul>