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copied!<p>For any element <code>array[i]</code>, you can determine if <code>i</code> points to a single byte character, the start of a 2-byte character, or the middle of a 2-byte character using the following test:</p> <p>Starting with <code>array[i-1]</code> count the number of contiguous MSB==1.</p> <p>If <code>array[i]</code> is preceded by an ODD number of 1's, then <code>array[i]</code> is the middle of a 2-byte array.</p> <p>If <code>array[i]</code> is preceded by an EVEN number of 1's, then if <code>MSB(array[i])</code> is 0, <code>array[i]</code> is a single byte character, otherwise <code>array[i]</code> is the start of a 2-byte character.</p> <p>Since we're trying to delete the character just before <code>array[i]</code>, once you determine if <code>array[i]</code> is the start or the middle of a character, then you have to run the same test for <code>array[i-x]</code>, where <code>x</code> is either 1 or 2 depending on if <code>array[i]</code> is pointing to the start or middle of a character, respectively.</p> <hr> <p>Edit (What happens when arr[0] is 1-byte, and arr[1] is 2-byte?):</p> <p>Firstly, more detail about the search for contiguous 1's: When counting contiguous 1's, the loop stops if we reach array[0], or MSB(array[j])==0.</p> <pre><code>odd=0 j = i while( j && MSB(arr[j-1]) ) j-=1 odd^=1 <<(binary XOR) </code></pre> <p>When the loop completes, odd will be 1 if there are an odd number of contiguous 1's and odd will be 0 if there are 0 or an even number of contiguous 1's.</p> <hr> <p>If we have an array with a 1-byte character in arr[0] and a 2-byte character in arr[1], then, supposedly, i can only have the values 0, 1, or 2.</p> <ul> <li>i=0: The loop never runs because i==0. We consider there to be an <strong>EVEN</strong> number of preceding 1's because odd==0. The MSB of arr[i] is 0, so <strong>arr[i] is the start of a 1-byte character</strong>.</li> <li>i=1: The loop never runs because MSB(arr[i-1]) is 0. We consider there to be an <strong>EVEN</strong> number of contiguous 1's because odd==0. The MSB of arr[i] is 1, so <strong>arr[i] is the start of a 2-byte character</strong>.</li> <li>i=2: The loop runs one time. We find an <strong>ODD</strong> number of consecutive 1's. Because there is an odd number of preceding 1's, <strong>arr[i] is the middle of a 2-byte character</strong>.</li> </ul>

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