217. Contains Duplicate
Easy
Given an array of integers, find if the array contains any duplicates.
Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.
Example 1:
Input: [1,2,3,1] Output: true
Example 2:
Input: [1,2,3,4] Output: false
Example 3:
Input: [1,1,1,3,3,4,3,2,4,2] Output: true
package leetcode.easy;
public class ContainsDuplicate {
public boolean containsDuplicate1(int[] nums) {
for (int i = 0; i < nums.length; ++i) {
for (int j = 0; j < i; ++j) {
if (nums[j] == nums[i]) {
return true;
}
}
}
return false;
}
// Time Limit Exceeded
public boolean containsDuplicate2(int[] nums) {
java.util.Arrays.sort(nums);
for (int i = 0; i < nums.length - 1; ++i) {
if (nums[i] == nums[i + 1]) {
return true;
}
}
return false;
}
public boolean containsDuplicate3(int[] nums) {
java.util.Set<Integer> set = new java.util.HashSet<>(nums.length);
for (int x : nums) {
if (set.contains(x)) {
return true;
} else {
set.add(x);
}
}
return false;
}
@org.junit.Test
public void test1() {
int[] nums1 = { 1, 2, 3, 1 };
int[] nums2 = { 1, 2, 3, 4 };
int[] nums3 = { 1, 1, 1, 3, 3, 4, 3, 2, 4, 2 };
System.out.println(containsDuplicate1(nums1));
System.out.println(containsDuplicate1(nums2));
System.out.println(containsDuplicate1(nums3));
}
@org.junit.Test
public void test2() {
int[] nums1 = { 1, 2, 3, 1 };
int[] nums2 = { 1, 2, 3, 4 };
int[] nums3 = { 1, 1, 1, 3, 3, 4, 3, 2, 4, 2 };
System.out.println(containsDuplicate2(nums1));
System.out.println(containsDuplicate2(nums2));
System.out.println(containsDuplicate2(nums3));
}
@org.junit.Test
public void test3() {
int[] nums1 = { 1, 2, 3, 1 };
int[] nums2 = { 1, 2, 3, 4 };
int[] nums3 = { 1, 1, 1, 3, 3, 4, 3, 2, 4, 2 };
System.out.println(containsDuplicate3(nums1));
System.out.println(containsDuplicate3(nums2));
System.out.println(containsDuplicate3(nums3));
}
}