I am facing a challenge with a sorted array of dates, here is an example:
let arr = ['2019-03-12', '2019-02-11', '2019-02-09', '2018-06-09', '2018-01-24', ..]The arr has a length of 100,000, and I need to filter this array using a binary search tree for performance reasons. However, I am unsure how to do this since a binary search tree typically returns an exact value, but I need to return all values that contain "2018", for instance.
Any suggestions on how I can achieve this?
To find the last occurrence of an element in a sorted array, you can utilize the upperBound method.
The Upper Bound function will return the index of the last occurrence of the specified element within the array.
const upperBound = (sortedArray, target) => {
let start = 0;
let end = sortedArray.length - 1;
let rightMostIndex = -1;
while (start <= end) {
const mid = Math.floor((end - start) / 2) + start;
if (sortedArray[mid] === target) {
rightMostIndex = Math.max(rightMostIndex, mid);
}
if (sortedArray[mid] >= target) {
start = mid + 1;
} else {
end = mid - 1;
}
}
return rightMostIndex;
};
For finding the leftmost occurrence of an element in a sorted array, you can apply the lowerBound approach:
const lowerBound = (sortedArray, target) => {
let start = 0;
let end = sortedArray.length - 1;
while (start <= end) {
const mid = Math.floor((end - start) / 2) + start;
if (sortedArray[mid] > target) {
end = mid - 1;
} else {
start = mid + 1;
}
}
return start;
};
Utilizing a binary search algorithm is an efficient way to retrieve a specific value from a dataset. In this scenario, you can repeatedly employ the method of splicing on the results obtained through the binary search process until all instances of 2018 have been removed.
The splice() function facilitates the addition or removal of items within an array while also providing the extracted item(s).
It is essential to retain the filtered values during this operation.
let data = ['2019-03-12', '2019-02-11', '2019-02-09', '2018-06-09', '2018-01-24', '2018-01-24'];
data.sort();
let updatedData = [];
let resultIndex = 0;
while (resultIndex !== -1) {
resultIndex = executeBinarySearch(data, '2018');
if (resultIndex !== -1) {
updatedData.push(data[resultIndex]);
data.splice(resultIndex, 1);
}
}
console.log(updatedData)
function executeBinarySearch(data, key) {
let start=0, end=data.length-1;
while (start <= end){
let mid = Math.floor((start + end) / 2);
if (data[mid].substring(0,4) === (key)) return mid;
else if (data[mid] < key)
start = mid + 1;
else
end = mid - 1;
}
return -1;
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