[英]Find all combinations of elements in an array
The problem I am trying to solve is that I want to generate an array which represents all combinations of elements in a source array. 我试图解决的问题是我想生成一个数组,该数组代表源数组中元素的所有组合。
Given an input of 2 items, there are 4 combinations (represented here as binary) 给定2个项目的输入,共有4种组合(此处表示为二进制)
Group 1 |
第1组| 0 |
0 | 1 |
1 | 0 |
0 | 1
1个
Group 2 |第2组| 0 |
0 | 0 |
0 | 1 |
1 | 1
1个
----------------------------------------------------
&Result |&结果| 0 |
0 | 1 |
1 | 2 |
2 | 3
3
This can be generalised so the number of combinations is 2 (number of groups) (So 3 groups has 8 combinations, 4 has 16 etc). 这可以被概括为组合数为2 (组数) (因此3个组具有8个组合,4个具有16个等)。
So the question is; 所以问题是; given a javascript array:
给定一个javascript数组:
var groups = [
{
name:"group1",
bit: 1
},
{
name:"group2",
bit: 2
},
{
name:"group3",
bit: 4
}];
I need to generate an array where the index represents the and'ing of the bit
property and the value of the array is arbitrary (further calculation - not relevant) so lets just make it an array of the group names (for the purpose of this question). 我需要生成一个数组,其中索引表示
bit
属性的和,并且数组的值是任意的(进一步的计算-不相关),因此仅使它成为组名称的数组即可(出于此目的)题)。 This result is desirable: 此结果是可取的:
var result = [
{groups: []}, //0
{groups: ["group1"]}, //1
{groups: ["group2"]}, //2
{groups: ["group1","group2"]}, //3
{groups: ["group3"]}, //4
{groups: ["group1","group3"]}, //5
{groups: ["group2","group3"]}, //6
{groups: ["group1","group2","group3"]} //7
]
You can see in the comments there that each index in the array represents the act of and'ing the bit
property from the original. 您可以在评论那里,阵列中的每个索引代表AND'ing的的行为见
bit
从原来的属性。
I have prepared a jsfiddle with the input and required output should it be useful in answering the question. 我准备了一个jsfiddle,其中包含输入和必需的输出,如果它对回答问题有用的话。
This is my current solution , based on mellamokb's answer but re-written in my prefered style. 这是我目前的解决方案 ,基于mellamokb的答案,但以我偏爱的风格重写。 I was hoping there was a more elegant solution as this has a lot of iterations over the array which are unecessary.
我希望有一个更优雅的解决方案,因为它在数组上有很多不必要的迭代。 Any better solutions?
有更好的解决方案吗?
var resultCount = Math.pow(2,groups.length);
var result = [];
for(var i=0;i<resultCount;i++){
result.push({
groups: $.map(groups, function(e,idx){
return ((i & Math.pow(2,idx)) != 0)
? e.name
: null
})
});
}
Here is a relatively efficient solution that builds up the arrays by index: 这是一个相对有效的解决方案,可通过索引构建数组:
var result = [];
var resultCount = Math.pow(2, groups.length);
for (var i = 0; i < resultCount; i++) {
result[i] = { groups: [] };
for (var g = 0; g < groups.length; g++) {
if (i & groups[g].bit) result[i].groups.push(groups[g].name);
}
}
Demo: http://jsfiddle.net/7ZsHL/9/ 演示: http : //jsfiddle.net/7ZsHL/9/
I think you can do it without having to store the bit and what not. 我认为您可以做到这一点而不必存储位和不存储什么。
var groups = [
"group1",
"group2",
"group3",
"group4"
];
var output = [];
for (var i = 0; i < Math.pow(2, groups.length); i++) {
var arr = [];
output.push(arr);
for (var j = 0; j < groups.length; j++) {
if (i & (Math.pow(2, j))) {
arr.push(groups[j]);
} else {
arr.push(0);
}
}
}
I like what others have done, but in a situation like this, I might choose to be a little mover verbose in my code, as the intent of the algorithm is hard to communicate. 我喜欢别人所做的事情,但是在这种情况下,由于算法的意图难以传达,因此我可能会选择在代码中稍加改动。
An Update Of Your Fiddle 小提琴的更新
var groups = [
{
name:"group1",
bit: 1
},
{
name:"group2",
bit: 2
},
{
name:"group3",
bit: 4
}];
function parseIterations(groups){
var aIterations = [];
var aBits = [];
var iGroups = groups.length;
var iTotalIterations = Math.pow(2, iGroups);
for (var i = 0; i < iTotalIterations; i++) {
var oIteration = { groups: [] };
for (var j = 0; j < iGroups; j++) {
if (typeof aBits[j] == 'undefined')
aBits[j] = true;
// while you could infer the .bit value from j,
// i've chosen to use your .bit value here.
aBits[j] = (i % groups[j].bit == 0) ? !aBits[j] : aBits[j];
if (aBits[j])
oIteration.groups.push(groups[j].name);
}
aIterations[i] = oIteration;
}
return aIterations;
}
var result = parseIterations(groups);
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