//取数组交集
doIntersection(firstArray, secondArray) {
// The logic here is to create a hashmap with the elements of the firstArray as the keys.
// After that, you can use the hashmap's O(1) look up time to check if the element exists in the hash
// If it does exist, add that element to the new array.
var hashmap = {};
var intersectionArray = [];
firstArray.forEach(function (element) {
hashmap[element] = 1;
});
// Since we only want to push unique elements in our case... we can implement a counter to keep track of what we already added
secondArray.forEach(function (element) {
if (hashmap[element] === 1) {
intersectionArray.push(element);
hashmap[element]++;
}
});
return intersectionArray;
// Time complexity O(n), Space complexity O(n)
},
//用法直接调用得到返回值便是交集值
this.doIntersection(arr1, arr2);