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Computing the union and intersection of two unsorted arrays in O(nlogm) time


Computing the union and intersection of two unsorted arrays in O(nlogm) time

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Computing the union and intersection of two unsorted arrays in O(nlogm) time
Tag : algorithm , By : Janne Laine
Date : November 25 2020, 07:06 PM

This might help you As vivek_23 said, you can do better using a hash table with high probability.
However, to achieve O(n log m), and assuming your sets are stored as arrays, you can sort A in O(m log m) time and then do n binary searches for each element of B to see if it is also in A. Each lookup takes O(log m) time, for a total of O(n log m) time.

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Union and Intersection of Arrays in Django


Tag : python , By : Nick
Date : March 29 2020, 07:55 AM
Hope this helps You can perform intersections and unions of set objects using the & and | operators:
intersection = queryset1 & queryset2

union = queryset1 | queryset2

C++set intersection and union using arrays


Tag : cpp , By : Priyatna Harun
Date : March 29 2020, 07:55 AM
With these it helps Use std::set_union and std::set_intersection, e.g.
int *c = std::set_union(setA, setA + a, setB, setB + b, setC)
int *c = std::set_intersection(setA, setA + a, setB, setB + b, setC)

Map arrays using union or intersection to produce a third array


Tag : javascript , By : Simone
Date : March 29 2020, 07:55 AM
it fixes the issue Here idea is
First change the second array to object so it becomes easier to find values on it Now loop through array1 and take the respective children from array2 Loop on children of array1 and change value according to children from array2
const arr1 = [{"name":"Category 1","value":"Vegetables","children":[{"name":"Carrots","value":"Carrots","count":2},{"name":"Peas","value":"Peas","count":1}]},{"name":"Category 2","value":"Fruits","children":[{"name":"Apples","value":"Apples","count":10},{"name":"Bananas","value":"Bananas","count":5}]},{"name":"Category 3","value":"Desserts","children":[{"name":"Ice Cream","value":"IceCream","count":3},{"name":"Cakes","value":"Cakes","count":3}]}];
const arr2 = [{"name":"Category 1","value":"Vegetables","children":[{"name":"Peas","value":"Peas","count":1}]},{"name":"Category 2","value":"Fruits","children":[{"name":"Apples","value":"Apples","count":3},{"name":"Bananas","value":"Bananas","count":2}]},{"name":"Category 3","value":"Desserts","children":[]}];
 
let arr2Obj = Object.fromEntries(arr2.map(val => [val.name, val]))

const res = arr1.map(({ name, value, children }) => {
  let arr2Children = ( arr2Obj[name] || {} ).children
  let childrenObj = Object.fromEntries(arr2Children.map(val => [val.name,val]))
  let newChildren = children.map( val => {
    let count = (childrenObj[val.name] || {}).count || 0
    return {...val,count}
  })
  return {name,value,children:newChildren}
});
console.log(res);
.as-console-wrapper { max-height: 100% !important; top: auto; }
const arr1 = [{"name":"Category 1","value":"Vegetables","children":[{"name":"Carrots","value":"Carrots","count":2},{"name":"Peas","value":"Peas","count":1}]},{"name":"Category 2","value":"Fruits","children":[{"name":"Apples","value":"Apples","count":10},{"name":"Bananas","value":"Bananas","count":5}]},{"name":"Category 3","value":"Desserts","children":[{"name":"Ice Cream","value":"IceCream","count":3},{"name":"Cakes","value":"Cakes","count":3}]}];
const arr2 = [{"name":"Category 1","value":"Vegetables","children":[{"name":"Peas","value":"Peas","count":1}]},{"name":"Category 2","value":"Fruits","children":[{"name":"Apples","value":"Apples","count":3},{"name":"Bananas","value":"Bananas","count":2}]},{"name":"Category 3","value":"Desserts","children":[]}];

let createObject = (arr) => arr.reduce((op,[key,value])=>{
  op[key] = value
  return op
},{})

let arr2Obj = createObject(arr2.map(val => [val.name, val]))

const res = arr1.map(({ name, value, children }) => {
  let arr2Children = ( arr2Obj[name] || {} ).children
  let childrenObj = createObject(arr2Children.map(val => [val.name,val]))
  let newChildren = children.map( val => {
    let count = (childrenObj[val.name] || {}).count || 0
    return {...val,count}
  })
  return {name,value,children:newChildren}
});
console.log(res);

Computing set intersection in linear time?


Tag : algorithm , By : matthew
Date : March 29 2020, 07:55 AM

intersection and union of n-arrays in C


Tag : c , By : user150694
Date : March 29 2020, 07:55 AM
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