计算1数组中元素的笛卡尔积

Question

I want to compute the cartesian product inside the single elements of an array. There should only be 2 values at a time.
So if this my array is:

[["cat dog mouse"], ["blue red green"]]

The expected value is:

• cat, dog
• cat, mouse
• dog, mouse
• blue, red
• blue, green
• red, green

This is my buggy approach:

var arr = [["cat dog mouse"], ["blue red green"], ["apple orange banana"]];

for (i = 0; i < arr.length; i++) {
    for(j = 0; j < arr[i].length; j++){
        if(j >= arr[i].length){
            console.log(arr[i][j].split( " ")  + " "  + arr[i][0])
        }else{
            console.log(arr[i][j].split( " ")  + " "  + arr[i][j+1])
        }
    }
}

It gives me

• cat,dog,mouse undefined
• blue,red,green undefined

Answer 1

You can do something like this using split() and for loop

 var arr = [ ["cat dog mouse"], ["blue red green"], ["apple orange banana"] ]; // iterate the array for (i = 0; i < arr.length; i++) { // split the string var inArr = arr[i][0].split(' '); // iterate the splitted string array for (j = 0; j < inArr.length - 1; j++) { // iterate string next to current string for (k = j + 1; k < inArr.length; k++) // generate the output console.log(inArr[j] + ', ' + inArr[k]); } } 

Answer 2

You were close, some modified code

var arr = [["cat dog mouse"], ["blue red green"], ["apple orange banana"]];

for (i = 0; i < arr.length; i++) {
    var items = arr[i][0].split(" ")
    for (j = 0; j < items.length - 1; j++) {
        for (k = j+1; k < items.length; k++) {
            console.log(items[j], items[k])
        }
    }
}

result:

cat dog
cat mouse
dog mouse
blue red
blue green
red green
apple orange
apple banana
orange banana

Answer 3

[["cat dog mouse"], ["blue red green"]].forEach(function (item) {
    item.forEach(function (value) {
         var arr = value.split(' ');
         var hash = {};
         arr.forEach(function (firstItem) {
              arr.forEach(function (secondItem) {
                  if (firstItem !== secondItem && !hash[firstItem + secondItem] && !hash[secondItem + firstItem]) {
                      console.log(firstItem + ', ' + secondItem);
                      hash[firstItem+secondItem] = true;
                  }
              });
         })
    });
});

Answer 4

A solution splited in partial solutions, one for the arrays and one for the combination without repeat.

 function combine(array, length) { function c(l, r) { var ll = l.slice(); if (r.length === length) { result.push(r); return; } while (ll.length) { c(ll, r.concat(ll.shift())); } } var result = []; c(array, []); return result; } function get(array) { return array.map(function (a) { return combine(a[0].split(' '), 2); }); } var result = get([["cat dog mouse"], ["blue red green"], ["apple orange banana"]]); document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>'); 

Answer 5

You can do it in functional way , just using .map() and .forEach() method :

var arr = [["cat dog mouse"], ["blue red green"], ["apple orange banana"]];


function print(item){
  //If there is one last item we stop the process
  if (item.length <= 1) return;
  else {
    //Retrieve head of our stack and shift the first item
    const head = item.shift();
    item.forEach((elm) => console.log(head + ',' + elm));
    // call our recursive function with the new array
    return print(item);
  }
}

function combine(arr){
  //Return array splited by using .map and .split operations, then iterate by using forEach and call our
  // recursive function
  arr
    .map((array) => array[0].split(' '))
    .forEach((value) => print(value));
}

combine(arr);

You can check the Plunker