Algorithm

Problem Name: 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] <= 10`

Code Examples

#1 Code Example with C Programming

```Code - C Programming```

``````
int cmp(const void *a, const void *b) {
return *(int *)a - *(int *)b;
}
bool containsDuplicate(int* nums, int numsSize) {
int i;

qsort(nums, numsSize, sizeof(int), cmp);

for (i = 1; i  <  numsSize; i ++) {
if (nums[i] == nums[i - 1]) return true;
}

return false;
}
``````
Copy The Code &

Input

cmd
nums = [1,2,3,1]

Output

cmd
true

#2 Code Example with Java Programming

```Code - Java Programming```

``````
class Solution {
public boolean containsDuplicate(int[] nums) {
return Arrays.stream(nums).boxed().collect(Collectors.toSet()).size() < nums.length;
}
}
``````
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Input

cmd
nums = [1,2,3,1]

Output

cmd
true

#3 Code Example with Javascript Programming

```Code - Javascript Programming```

``````
const containsDuplicate = function(nums) {
const hash = {};
for (let el of nums) {
if (hash.hasOwnProperty(el)) {
return true;
} else {
hash[el] = 1;
}
}
return false;
};
``````
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Input

cmd
nums = [1,2,3,4]

Output

cmd
false

#4 Code Example with Python Programming

```Code - Python Programming```

``````
class Solution:
def containsDuplicate(self, nums):
"""
:type nums: List[int]
:rtype: bool
"""
dic=dict()
for num in nums:
if not num in dic:
dic[num]=1
else:
return True
return False
``````
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Input

cmd
nums = [1,2,3,4]

Output

cmd
false

#5 Code Example with C# Programming

```Code - C# Programming```

``````
using System.Collections.Generic;

namespace LeetCode
{
public class _0217_ContainsDuplicate
{
public bool ContainsDuplicate(int[] nums)
{
var set = new HashSet < int>();
foreach (var num in nums)
{
if (set.Contains(num)) return true;
}
return false;
}
}
}
``````
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Input

cmd
nums = [1,1,1,3,3,4,3,2,4,2]

Output

cmd
true