用javascript实现数组交叉的最简单、无库代码是什么?我想写
intersection([1,2,3], [2,3,4,5])
并获得
[2, 3]
用javascript实现数组交叉的最简单、无库代码是什么?我想写
intersection([1,2,3], [2,3,4,5])
并获得
[2, 3]
当前回答
希望这有助于所有版本。
function diffArray(arr1, arr2) {
var newArr = [];
var large = arr1.length>=arr2.length?arr1:arr2;
var small = JSON.stringify(large) == JSON.stringify(arr1)?arr2:arr1;
for(var i=0;i<large.length;i++){
var copyExists = false;
for(var j =0;j<small.length;j++){
if(large[i]==small[j]){
copyExists= true;
break;
}
}
if(!copyExists)
{
newArr.push(large[i]);
}
}
for(var i=0;i<small.length;i++){
var copyExists = false;
for(var j =0;j<large.length;j++){
if(large[j]==small[i]){
copyExists= true;
break;
}
}
if(!copyExists)
{
newArr.push(small[i]);
}
}
return newArr;
}
其他回答
另一种可以同时处理任意数量数组的索引方法:
// Calculate intersection of multiple array or object values.
function intersect (arrList) {
var arrLength = Object.keys(arrList).length;
// (Also accepts regular objects as input)
var index = {};
for (var i in arrList) {
for (var j in arrList[i]) {
var v = arrList[i][j];
if (index[v] === undefined) index[v] = 0;
index[v]++;
};
};
var retv = [];
for (var i in index) {
if (index[i] == arrLength) retv.push(i);
};
return retv;
};
它只适用于可以作为字符串计算的值,你应该将它们作为一个数组传递:
intersect ([arr1, arr2, arr3...]);
...但它透明地接受对象作为参数或任何要交叉的元素(总是返回公共值的数组)。例子:
intersect ({foo: [1, 2, 3, 4], bar: {a: 2, j:4}}); // [2, 4]
intersect ([{x: "hello", y: "world"}, ["hello", "user"]]); // ["hello"]
编辑:我只是注意到,这是,在某种程度上,有点bug。
也就是说:我在编码时认为输入数组本身不能包含重复(正如所提供的示例那样)。
但如果输入数组恰好包含重复,就会产生错误的结果。示例(使用下面的实现):
intersect ([[1, 3, 4, 6, 3], [1, 8, 99]]);
// Expected: [ '1' ]
// Actual: [ '1', '3' ]
幸运的是,这很容易通过添加二级索引来解决。那就是:
变化:
if (index[v] === undefined) index[v] = 0;
index[v]++;
by:
if (index[v] === undefined) index[v] = {};
index[v][i] = true; // Mark as present in i input.
,:
if (index[i] == arrLength) retv.push(i);
by:
if (Object.keys(index[i]).length == arrLength) retv.push(i);
完整的例子:
// Calculate intersection of multiple array or object values.
function intersect (arrList) {
var arrLength = Object.keys(arrList).length;
// (Also accepts regular objects as input)
var index = {};
for (var i in arrList) {
for (var j in arrList[i]) {
var v = arrList[i][j];
if (index[v] === undefined) index[v] = {};
index[v][i] = true; // Mark as present in i input.
};
};
var retv = [];
for (var i in index) {
if (Object.keys(index[i]).length == arrLength) retv.push(i);
};
return retv;
};
intersect ([[1, 3, 4, 6, 3], [1, 8, 99]]); // [ '1' ]
如果只使用关联数组呢?
function intersect(a, b) {
var d1 = {};
var d2 = {};
var results = [];
for (var i = 0; i < a.length; i++) {
d1[a[i]] = true;
}
for (var j = 0; j < b.length; j++) {
d2[b[j]] = true;
}
for (var k in d1) {
if (d2[k])
results.push(k);
}
return results;
}
编辑:
// new version
function intersect(a, b) {
var d = {};
var results = [];
for (var i = 0; i < b.length; i++) {
d[b[i]] = true;
}
for (var j = 0; j < a.length; j++) {
if (d[a[j]])
results.push(a[j]);
}
return results;
}
破坏性似乎是最简单的,特别是如果我们可以假设输入是排序的:
/* destructively finds the intersection of
* two arrays in a simple fashion.
*
* PARAMS
* a - first array, must already be sorted
* b - second array, must already be sorted
*
* NOTES
* State of input arrays is undefined when
* the function returns. They should be
* (prolly) be dumped.
*
* Should have O(n) operations, where n is
* n = MIN(a.length, b.length)
*/
function intersection_destructive(a, b)
{
var result = [];
while( a.length > 0 && b.length > 0 )
{
if (a[0] < b[0] ){ a.shift(); }
else if (a[0] > b[0] ){ b.shift(); }
else /* they're equal */
{
result.push(a.shift());
b.shift();
}
}
return result;
}
非破坏性的要稍微复杂一点,因为我们要跟踪指标:
/* finds the intersection of
* two arrays in a simple fashion.
*
* PARAMS
* a - first array, must already be sorted
* b - second array, must already be sorted
*
* NOTES
*
* Should have O(n) operations, where n is
* n = MIN(a.length(), b.length())
*/
function intersect_safe(a, b)
{
var ai=0, bi=0;
var result = [];
while( ai < a.length && bi < b.length )
{
if (a[ai] < b[bi] ){ ai++; }
else if (a[ai] > b[bi] ){ bi++; }
else /* they're equal */
{
result.push(a[ai]);
ai++;
bi++;
}
}
return result;
}
最简单、最快的O(n)和最短的方式:
函数交点(a, b) { const setA = new Set(a); 返回b.filter(value => setA.has(value)); } console.log(十字路口([1,2,3],[2、3、4、5)))
@nbarbosa几乎有相同的答案,但他将两个数组强制转换为Set,然后再转换回数组。不需要任何额外的选角。
Var数组= [ [1,2,3], [2,3,4,5] ] 函数commonValue(…arr) { 令res = arr[0]。过滤(函数(x) { 返回arr.every((y) => y.includes(x)) }) 返回res; } commonValue数组(…);