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@AleksandrChukhray
Created September 2, 2020 15:52
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// Merge Sort Implentation (Recursion)
function mergeSort (unsortedArray) {
// No need to sort the array if the array only has one element or empty
if (unsortedArray.length <= 1) {
return unsortedArray;
}
// In order to divide the array in half, we need to figure out the middle
const middle = Math.floor(unsortedArray.length / 2);
// This is where we will be dividing the array into left and right
const left = unsortedArray.slice(0, middle);
const right = unsortedArray.slice(middle);
// Using recursion to combine the left and right
return merge(
mergeSort(left), mergeSort(right)
);
}
// Merge the two arrays: left and right
function merge (left, right) {
let resultArray = [], leftIndex = 0, rightIndex = 0;
// We will concatenate values into the resultArray in order
while (leftIndex < left.length && rightIndex < right.length) {
if (left[leftIndex] < right[rightIndex]) {
resultArray.push(left[leftIndex]);
leftIndex++; // move left array cursor
} else {
resultArray.push(right[rightIndex]);
rightIndex++; // move right array cursor
}
}
// We need to concat here because there will be one element remaining
// from either left OR the right
return resultArray
.concat(left.slice(leftIndex))
.concat(right.slice(rightIndex));
}
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