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
代码
Approach #1 (Naive Linear Search) [Time Limit Exceeded]
class Solution {
public boolean containsDuplicate(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;
}
}
Approach #2 Sorting
class Solution {
public boolean containsDupliate(int[] nums) {
Arrays.sort(nums);
for (int i = 0; i < nums.length - 1; i++) {
if (nums[i] == nums[i + 1]) {
return true;
}
}
return false;
}
}
Approach #3 Hash Table
class Solution {
public boolean containsDuplicate(int[] nums) {
Set<Integer> set = new HashSet<>(nums.length);
for (int num: nums) {
if (set.contains(num)) {
return true;
}
}
return false;
}
}