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LeetCode_349. Intersection of Two Arrays
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349. Intersection of Two Arrays
Easy
Given two arrays, write a function to compute their intersection.
Example 1:
Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]
Example 2:
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]
Note:
- Each element in the result must be unique.
- The result can be in any order.
package leetcode.easy;
public class IntersectionOfTwoArrays {
public int[] set_intersection(java.util.HashSet<Integer> set1, java.util.HashSet<Integer> set2) {
int[] output = new int[set1.size()];
int idx = 0;
for (Integer s : set1) {
if (set2.contains(s)) {
output[idx++] = s;
}
}
return java.util.Arrays.copyOf(output, idx);
}
public int[] intersection1(int[] nums1, int[] nums2) {
java.util.HashSet<Integer> set1 = new java.util.HashSet<Integer>();
for (Integer n : nums1) {
set1.add(n);
}
java.util.HashSet<Integer> set2 = new java.util.HashSet<Integer>();
for (Integer n : nums2) {
set2.add(n);
}
if (set1.size() < set2.size()) {
return set_intersection(set1, set2);
} else {
return set_intersection(set2, set1);
}
}
public int[] intersection2(int[] nums1, int[] nums2) {
java.util.HashSet<Integer> set1 = new java.util.HashSet<Integer>();
for (Integer n : nums1) {
set1.add(n);
}
java.util.HashSet<Integer> set2 = new java.util.HashSet<Integer>();
for (Integer n : nums2) {
set2.add(n);
}
set1.retainAll(set2);
int[] output = new int[set1.size()];
int idx = 0;
for (int s : set1) {
output[idx++] = s;
}
return output;
}
@org.junit.Test
public void test1() {
int[] nums1 = { 1, 2, 2, 1 };
int[] nums2 = { 2, 2 };
int[] result = intersection1(nums1, nums2);
for (int i = 0; i < result.length; i++) {
System.out.print(result[i] + " ");
}
System.out.println();
result = intersection2(nums1, nums2);
for (int i = 0; i < result.length; i++) {
System.out.print(result[i] + " ");
}
System.out.println();
}
@org.junit.Test
public void test2() {
int[] nums1 = { 4, 9, 5 };
int[] nums2 = { 9, 4, 9, 8, 4 };
int[] result = intersection1(nums1, nums2);
for (int i = 0; i < result.length; i++) {
System.out.print(result[i] + " ");
}
System.out.println();
result = intersection2(nums1, nums2);
for (int i = 0; i < result.length; i++) {
System.out.print(result[i] + " ");
}
System.out.println();
}
}
