README.md

961. N-Repeated Element in Size 2N Array

In a array A of size 2N, there are N+1 unique elements, and exactly one of these elements is repeated N times.

Return the element repeated N times.

Example 1:

Input: [1,2,3,3]
Output: 3

Example 2:

Input: [2,1,2,5,3,2]
Output: 2

Example 3:

Input: [5,1,5,2,5,3,5,4]
Output: 5

Note:

1. 4 <= A.length <= 10000
2. 0 <= A[i] < 10000
3. A.length is even

Solutions (Rust)

1. Set

use std::collections::HashSet;

impl Solution {
    pub fn repeated_n_times(a: Vec<i32>) -> i32 {
        let mut set = HashSet::new();

        for n in a {
            if set.contains(&n) {
                return n;
            } else {
                set.insert(n);
            }
        }

        -1
    }
}

2. Compare

impl Solution {
    pub fn repeated_n_times(a: Vec<i32>) -> i32 {
        for i in 1..4 {
            for j in i..a.len() {
                if a[j - i] == a[j] {
                    return a[j];
                }
            }
        }

        -1
    }
}