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Count_Unique_Values_MP.js
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Count_Unique_Values_MP.js
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// Input...
// Array - undefined, of any size
// Positive or Negative numbers
// Sorted -> most impor
// Output...
// Unique values
// Count, not items.
// O(n) runtime and O(1) space
function uniqueCounter(array) {
if (!array || array.length === 0)
return 0
// Frequency counter is of no use, because the elements are sorteed.
// Keep moving the pointers, only changing the count once we have a new item.
let count = 1
// Create 2 pointers, side by side of each other.
// Iterate over the array for each pointer till we reach end of it.
// Move the 2nd pointer to each location.
// 1st pointer to be moved only when we have a new item.
for (let uniquePointer = 0, iterPointer = 0; iterPointer < array.length; iterPointer++) {
if(array[iterPointer] !== array[uniquePointer]) {
count++
uniquePointer = iterPointer
}
}
return count
}
clear()
console.log(uniqueCounter())
console.log(uniqueCounter([]))
console.log(uniqueCounter([1]))
console.log(uniqueCounter([1, 1]))
console.log(uniqueCounter([1, 1, 2, 2, 3]))
function uniqueCounter1(array) {
// Do inplace mutation.
// Create a pointer to iterate throught the entire array
// for each element if there is a unique position, move the counter array and do inaplace mutation for next comparson
if (!array || array.length === 0)
return 0
for (let counterPointer = 0, iterPointer = 0; iterPointer < array.length; iterPointer++) {
if (array[iterPointer] !== array[counterPointer]) {
counterPointer++
array[counterPointer] = array[iterPointer]
}
}
return countterPointer + 1
}
console.log("=======")
console.log(uniqueCounter1())
console.log(uniqueCounter1([]))
console.log(uniqueCounter1([1]))
console.log(uniqueCounter1([1, 1]))
console.log(uniqueCounter([1, 1, 2, 2, 3]))