217-ContainsDuplicate.md

217. Contains Duplicate

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Example 1:

Input: nums = [1,2,3,1]
Output: true

Example 2:

Input: nums = [1,2,3,4]
Output: false

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

Constraints:

1 <= nums.length <= 105
-109 <= nums[i] <= 109

Solution

• loop 比對並使用 hash

code

• java

  • Code

    class Solution {
      public boolean containsDuplicate_hash(int[] nums) {
          HashMap<Integer,Integer> resultMap = new HashMap<Integer, Integer>();
          for (int i: nums){
              if (resultMap.containsKey(i)){
                  return true;
              }
              resultMap.put(i,1);
          }
          return false;
      }
    
      public static boolean containsDuplicate_sorted(int[] nums) {
          Arrays.sort(nums);
          for (int i = 1; i < nums.length; i++) {
              if (nums[i] == nums[i - 1]) {
                  return true;
              }
          }
          return false;
      }
    }