Deleting arrays of same elements in 2 dimensional array in Javascript-CodePudding

I am wondering how you would go about deleting arrays that contain the same elements in a 2 dimensional array.

For example:

let 2dArr = [ [1, 2, 3],
              [3, 2, 1],
              [2, 4, 5],
              [4, 5, 2],
              [4, 3, 1] ];

This array would delete the second and fourth elements, returning the 2d array:

returnedArr = [ [1, 2, 3],
                [2, 4, 5],
                [4, 3, 1] ];

How exactly could this be done, preserving the 2d array? I could only think to loop through elements, comparing elements via a sort, and deleting them as you go along, but this would result in an indexing error if an element is deleted.

CodePudding user response：

1) You can easily achieve the result using reduce and Set as:

let twodArr = [
  [1, 2, 3],
  [3, 2, 1],
  [2, 4, 5],
  [4, 5, 2],
  [4, 3, 1],
];

const set = new Set();

const result = twodArr.reduce((acc, curr) => {
  const key = [...curr].sort((a, b) => a - b).join();
  if (!set.has(key)) {
    set.add(key);
    acc.push(curr);
  }
  return acc;
}, []);

console.log(result);

2) You can also use filter as:

let twodArr = [
  [1, 2, 3],
  [3, 2, 1],
  [2, 4, 5],
  [4, 5, 2],
  [4, 3, 1],
];

const set = new Set();

const result = twodArr.filter((curr) => {
  const key = [...curr].sort((a, b) => a - b).join();
  return !set.has(key) ? (set.add(key), true) : false;
});

console.log(result);

CodePudding user response：

You can use hash map

let arr = [ [1, 2, 3], [3, 2, 1],[2, 4, 5],[4, 5, 2],[4, 3, 1] ];
let obj = {}
let final = []

for(let i=0; i<arr.length; i  ){
  // create a key
  let sorted = [...arr[i]].sort((a,b)=> a- b).join`,`
  // check if this is not present in our hash map
  // add value to final out and update hash map accordingly
  if(!obj[sorted]){
    obj[sorted] = true
    final.push(arr[i])
  }
}

console.log(final)

CodePudding user response：

Using Array.prototype.filter() and a Set as thisArg

let arr = [ [1, 2, 3],
              [3, 2, 1],
              [2, 4, 5],
              [4, 5, 2],
              [4, 3, 1] ];


let res = arr.filter(function(e){
    const sorted = [...e].sort((a,b) => a-b).join('|');
    return this.has(sorted) ? false : this.add(sorted)    
},new Set)

console.log(res)