349. Intersection of Two Arrays【双指针|二分】

2017/3/23 15:41:47

Given two arrays, write a function to compute their intersection.

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].

Note:

• Each element in the result must be unique.
• The result can be in any order.

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作弊版：Python

class Solution(object):
    def intersection(self, nums1, nums2):
        return list(set( nums1 ) & set(nums2))

 

版本1：Java  O(m*n)  循环检查  

public class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        Set<Integer> set = new HashSet<Integer>();
        for ( int i=0;i<nums1.length;i++ )
            for ( int j=0;j<nums2.length;j++ )
                if ( nums1[i] == nums2[j] ){
                    set.add(nums1[i]);
                    break;
                }
        Object[] obj = set.toArray();
        int[] rs = new int[obj.length];
        for ( int i=0;i<obj.length;i++ )
        	rs[i] = (int)obj[i];
        return rs;
    }
}

 

版本2：Java  O(m+n)  借助哈希表+Set，或者双Set

public int[] intersection(int[] nums1, int[] nums2) {
		Map<Integer,Boolean> map = new Hashtable<Integer,Boolean>();
		Set<Integer> set = new TreeSet<Integer>();
        for ( int i=0;i<nums1.length;i++ )
            map.put( nums1[i] , true );
        for ( int j=0;j<nums2.length;j++ ){
        	if (map.get(nums2[j]) == null ) continue;
        	set.add(nums2[j]);
        }
        int i = 0;
        int[] rs = new int[set.size()];
        for ( Integer num : set )
        	rs[i++] = num;
        return rs;
    }