leetcode IntersectionofTwoArraysII
z
 2019-04-09 10:36:27   
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import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;

public class IntersectionofTwoArraysII {
  /**
   * Given two arrays, write a function to compute their intersection.
   *
   * Example 1:
   *
   * Input: nums1 = [1,2,2,1], nums2 = [2,2]
   * Output: [2,2]
   * Example 2:
   *
   * Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
   * Output: [4,9]
   * Note:
   *
   * Each element in the result should appear as many times as it shows in both arrays.
   * The result can be in any order.
   * Follow up:
   *
   * What if the given array is already sorted? How would you optimize your algorithm?
   * What if nums1's size is small compared to nums2's size? Which algorithm is better?
   * What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?
   */
  // sort version
  public int[] intersect(int[] nums1, int[] nums2) {
    Arrays.sort(nums1);
    Arrays.sort(nums2);
    int i=0;
    int j=0;
    LinkedList<Integer> l = new LinkedList<>();
    while(i<nums1.length && j<nums2.length){
      if (nums1[i] == nums2[j]){
        l.add(nums1[i]);
        while(i+1<nums1.length && nums1[i+1] == nums2[i])
          i++;
        while(j+1<nums2.length && nums2[j+1] == nums2[j])
          j++;
      }
      else if (nums1[i] < nums2[j]){
        i++;
      }
      else
        j++;
    }
    int[] res = new int[l.size()];
    for (int k=0; k<l.size(); k++){
      res[k] = l.get(k);
    }
    return res;
  }

  // there is a non-sort version, using a
  public int[] intesectII(int[] nums1, int[] nums2){
    LinkedList<Integer> dic = new LinkedList<>();
    LinkedList<Integer> res = new LinkedList<>();
    for (int i=0; i<nums1.length; i++){
      dic.add(nums1[i]);
    }
    for (int i=0; i<nums2.length; i++){
      boolean success = dic.remove(new Integer(nums2[i]));
      if (!success){
        res.add(nums2[i]);
      }
    }

    int[] r = new int[res.size()];
    for (int i=0; i<res.size(); i++){
      r[i] = res.get(i);
    }
    return r;
  }



}