4. There are duplicate elements
Given an integer array, determine whether there are duplicate elements.
If there is a value that appears at least twice in the array, the function returns true. If every element in the array is different, false is returned.
Method 1: Mine, but beyond the time limit
class Solution {
public boolean containsDuplicate(int[] nums) {
int length = nums.length;
for(int i=0;i<length;i++){
for(int j=i+1;j<length;j++){
if(nums[i]==nums[j]){
return true;
}
}
}
return false;
}
}
Method 2: Mine, after sorting first, compare adjacent ones
class Solution {
public boolean containsDuplicate(int[] nums) {
//排序
Arrays.sort(nums);
if(nums.length <=1){
return false;
}
for(int i=0;i<nums.length-1;i++){
if(nums[i] == nums[i+1]){
return true;
}
}
return false;
}
}
Method 3: Official Answer-Hash Table
class Solution {
public boolean containsDuplicate(int[] nums) {
Set<Integer> set = new HashSet<Integer>();
for (int x : nums) {
if (!set.add(x)) {
return true;
}
}
return false;
}
}
作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/contains-duplicate/solution/cun-zai-zhong-fu-yuan-su-by-leetcode-sol-iedd/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。