README.md

217. Contains Duplicate

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

Solutions (Rust)

1. Set-len

use std::collections::HashSet;

impl Solution {
    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
        nums.len() > nums.iter().collect::<HashSet<_>>().len()
    }
}

2. Linear Scan

impl Solution {
    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
        let len = nums.len();
        for i in 0..len {
            for j in (i + 1)..len {
                if nums[i] == nums[j] {
                    return true;
                }
            }
        }
        false
    }
}

3. Set-contains

use std::collections::HashSet;

impl Solution {
    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
        let mut set = HashSet::new();
        for n in nums {
            if set.contains(&n) {
                return true;
            } else {
                set.insert(n);
            }
        }
        false
    }
}

4. Sort

impl Solution {
    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
        let mut nums = nums;
        nums.sort_unstable();
        for i in 1..nums.len() {
            if nums[i - 1] == nums[i] {
                return true;
            }
        }
        false
    }
}