我有两个数组:
var array1 = ["A", "B", "C"];
var array2 = ["1", "2", "3"];
如何设置另一个数组以包含上述所有组合,以便:
var combos = ["A1", "A2", "A3", "B1", "B2", "B3", "C1", "C2", "C3"];
我有两个数组:
var array1 = ["A", "B", "C"];
var array2 = ["1", "2", "3"];
如何设置另一个数组以包含上述所有组合,以便:
var combos = ["A1", "A2", "A3", "B1", "B2", "B3", "C1", "C2", "C3"];
或者,如果您想使用任意数量的任意大小的数组创建组合...(我确定您可以递归地执行此操作,但是由于这不是求职面试,我改为使用迭代“ odometer”为此......它根据每个数组的长度增加一个“数字”,每个数字都是一个“base-n”数字)......例如......
combineArrays([ ["A","B","C"],
["+", "-", "*", "/"],
["1","2"] ] )
...返回...
[
"A+1","A+2","A-1", "A-2",
"A*1", "A*2", "A/1", "A/2",
"B+1","B+2","B-1", "B-2",
"B*1", "B*2", "B/1", "B/2",
"C+1","C+2","C-1", "C-2",
"C*1", "C*2", "C/1", "C/2"
]
...每一个都对应一个“里程表”值,从每个数组中选择一个索引......
[0,0,0], [0,0,1], [0,1,0], [0,1,1]
[0,2,0], [0,2,1], [0,3,0], [0,3,1]
[1,0,0], [1,0,1], [1,1,0], [1,1,1]
[1,2,0], [1,2,1], [1,3,0], [1,3,1]
[2,0,0], [2,0,1], [2,1,0], [2,1,1]
[2,2,0], [2,2,1], [2,3,0], [2,3,1]
“里程表”方法允许您轻松生成所需的输出类型,而不仅仅是像我们这里那样的连接字符串。除此之外,通过避免递归,我们避免了——我敢说吗?--堆栈溢出...
function combineArrays( array_of_arrays ){
// First, handle some degenerate cases...
if( ! array_of_arrays ){
// Or maybe we should toss an exception...?
return [];
}
if( ! Array.isArray( array_of_arrays ) ){
// Or maybe we should toss an exception...?
return [];
}
if( array_of_arrays.length == 0 ){
return [];
}
for( let i = 0 ; i < array_of_arrays.length; i++ ){
if( ! Array.isArray(array_of_arrays[i]) || array_of_arrays[i].length == 0 ){
// If any of the arrays in array_of_arrays are not arrays or zero-length, return an empty array...
return [];
}
}
// Done with degenerate cases...
// Start "odometer" with a 0 for each array in array_of_arrays.
let odometer = new Array( array_of_arrays.length );
odometer.fill( 0 );
let output = [];
let newCombination = formCombination( odometer, array_of_arrays );
output.push( newCombination );
while ( odometer_increment( odometer, array_of_arrays ) ){
newCombination = formCombination( odometer, array_of_arrays );
output.push( newCombination );
}
return output;
}/* combineArrays() */
// Translate "odometer" to combinations from array_of_arrays
function formCombination( odometer, array_of_arrays ){
// In Imperative Programmingese (i.e., English):
// let s_output = "";
// for( let i=0; i < odometer.length; i++ ){
// s_output += "" + array_of_arrays[i][odometer[i]];
// }
// return s_output;
// In Functional Programmingese (Henny Youngman one-liner):
return odometer.reduce(
function(accumulator, odometer_value, odometer_index){
return "" + accumulator + array_of_arrays[odometer_index][odometer_value];
},
""
);
}/* formCombination() */
function odometer_increment( odometer, array_of_arrays ){
// Basically, work you way from the rightmost digit of the "odometer"...
// if you're able to increment without cycling that digit back to zero,
// you're all done, otherwise, cycle that digit to zero and go one digit to the
// left, and begin again until you're able to increment a digit
// without cycling it...simple, huh...?
for( let i_odometer_digit = odometer.length-1; i_odometer_digit >=0; i_odometer_digit-- ){
let maxee = array_of_arrays[i_odometer_digit].length - 1;
if( odometer[i_odometer_digit] + 1 <= maxee ){
// increment, and you're done...
odometer[i_odometer_digit]++;
return true;
}
else{
if( i_odometer_digit - 1 < 0 ){
// No more digits left to increment, end of the line...
return false;
}
else{
// Can't increment this digit, cycle it to zero and continue
// the loop to go over to the next digit...
odometer[i_odometer_digit]=0;
continue;
}
}
}/* for( let odometer_digit = odometer.length-1; odometer_digit >=0; odometer_digit-- ) */
}/* odometer_increment() */
以防万一有人正在寻找Array.map
解决方案
var array1=["A","B","C"];
var array2=["1","2","3","4"];
console.log(array1.flatMap(d => array2.map(v => d + v)))
这种形式的循环
combos = [] //or combos = new Array(2);
for(var i = 0; i < array1.length; i++)
{
for(var j = 0; j < array2.length; j++)
{
//you would access the element of the array as array1[i] and array2[j]
//create and array with as many elements as the number of arrays you are to combine
//add them in
//you could have as many dimensions as you need
combos.push(array1[i] + array2[j])
}
}
for
在所有答案中看到很多循环......
这是我想出的递归解决方案,它将通过从每个数组中取出 1 个元素来找到 N 个数组的所有组合:
const array1=["A","B","C"]
const array2=["1","2","3"]
const array3=["red","blue","green"]
const combine = ([head, ...[headTail, ...tailTail]]) => {
if (!headTail) return head
const combined = headTail.reduce((acc, x) => {
return acc.concat(head.map(h => `${h}${x}`))
}, [])
return combine([combined, ...tailTail])
}
console.log('With your example arrays:', combine([array1, array2]))
console.log('With N arrays:', combine([array1, array2, array3]))
假设您使用的是最近支持的 Web 浏览器Array.forEach
:
var combos = [];
array1.forEach(function(a1){
array2.forEach(function(a2){
combos.push(a1 + a2);
});
});
如果您没有forEach
,那么在没有它的情况下重写它是一个足够简单的练习。正如其他人之前已经证明的那样,不这样做也有一些性能优势......(虽然我认为不久之后,常见的 JavaScript 运行时将优化掉任何当前的优势,否则这样做。)