Dear Moderator:
The original question that is being flagged as a duplicate fails to elaborate on several key issues.
- Unlike the other question, this query delves into not just how the operators technically work, but rather their specific function within the algorithm: why these operators are utilized at that particular point in the code.
- This unique question also includes an inquiry about the bit-wise comparison '&' operator, which was completely overlooked in the previous discussion.
- The core concept highlighted in the provided solution involves creating a bitmask by setting
. This effectively transforms the iterator 'i' in the loop into a binary vector, enabling a targeted evaluation against a specified 'j' value for inclusion in the testing sum.combinationsCount = 1 << listSize
This algorithm appears to offer a solution to a variation of the coin change problem. While the code seems functional based on my assessment, I am struggling to comprehend the significance of the final if statement check:
if (i & (1 << j)) {
combinationSum += arr[j];
}
I encountered this while following a tutorial and would greatly appreciate a breakdown of its role in the overall logic of the code.
UPDATE:
To clarify, I have a good grasp of HOW the operators are performing, such as the bit shifting and bitwise addition. What I seek to understand is their specific functionality within the operational flow of the algorithm.
possibleCombinationSumN(arr, n) {
if (arr.indexOf(n) >= 0) {
return true;
}
if (arr[0] > n) {
return false;
}
if (arr[arr.length - 1] > n) {
arr.pop();
return possibleCombinationSumN(arr, n);
}
var listSize = arr.length, combinationsCount = (1 << listSize)
for (var i = 1; i < combinationsCount; i++) {
var combinationSum = 0;
for (var j = 0; j < listSize; j++) {
if (i & (1 << j)) {
combinationSum += arr[j];
}
}
if (n === combinationSum) {
return true;
}
}
return false;
};