function IncrementBigNum($bigNumString)
{
$lastIndex = strlen($bigNumString) - 1;
if ($bigNumString[$lastIndex] != 9) {
$numberToIncrement = CharToInt($bigNumString[$lastIndex]);
++$numberToIncrement;
$bigNumString[$lastIndex] = IntToChar($numberToIncrement);
} else {
if (CheckForAllNines($bigNumString)) {
for ($r = 0; $r < $lastIndex + 1; $r++) {
$bigNumString[$r] = "0";
}
$bigNumString = "1" . $bigNumString;
} else {
$indexFirstNonNine = GetFirstNonNine($bigNumString);
$numberToIncrement = CharToInt($bigNumString[$indexFirstNonNine]);
++$numberToIncrement;
$bigNumString[$indexFirstNonNine] = IntToChar($numberToIncrement);
for ($d = $indexFirstNonNine + 1; $d < $lastIndex + 1; $d++) {
$bigNumString[$d] = "0";
}
}
}
echo "Result: " . $bigNumString . "\n";
}
/**
* This function takes a string representing a large number,
* increments it by 1, and returns the result
*
* @param array $bigNumString A string representation of a large number
*
* @return array $bigNumString large number string after increment
*/
function IncrementBigNum($bigNumString)
{
//Get the last index of the string
$lastIndex = strlen($bigNumString) - 1;
//Simply increment the last number if it is not nine
if ($bigNumString[$lastIndex] != 9) {
//Convert last number to an integer to allow increment
$numberToIncrement = CharToInt($bigNumString[$lastIndex]);
++$numberToIncrement;
//Revert integer to a char and replace in string/array
$bigNumString[$lastIndex] = IntToChar($numberToIncrement);
} else {
if (CheckForAllNines($bigNumString)) {
//Set all numbers in large number string to zero
for ($r = 0; $r < $lastIndex + 1; $r++) {
$bigNumString[$r] = "0";
}
//Prepend a one to large number string (eg. "999" becomes "1000")
$bigNumString = "1" . $bigNumString;
} else {
//Find the first non-nine number in the large string
$indexFirstNonNine = GetFirstNonNine($bigNumString);
//Increment the number
$numberToIncrement = CharToInt($bigNumString[$indexFirstNonNine]);
++$numberToIncrement;
//Replace the number incremented number in the large number string
$bigNumString[$indexFirstNonNine] = IntToChar($numberToIncrement);
//Set everything left of incremented number to zero
for ($d = $indexFirstNonNine + 1; $d < $lastIndex + 1; $d++) {
$bigNumString[$d] = "0";
}
}
}
//Return large number string after performing arithmetic
return $bigNumString;
}
