Question

How to find the length of the longest consecutive sequence of an unsorted vector of integers in Rust

Answer 1

use std::collections::HashSet;

fn longest_consecutive(nums: Vec<i32>) -> i32 {
    let num_set: HashSet<i32> = nums.into_iter().collect();
    let mut longest_streak = 0;

    for &num in &num_set {
        // Check if it's the start of a sequence
        if !num_set.contains(&(num - 1)) {
            let mut current_num = num;
            let mut current_streak = 1;

            // Count the length of the sequence
            while num_set.contains(&(current_num + 1)) {
                current_num += 1;
                current_streak += 1;
            }

            longest_streak = longest_streak.max(current_streak);
        }
    }

    longest_streak
}

fn main() {
    let nums = vec![680, 4, 590, 3, 1, 2];
    
    println!("Longest consecutive sequence length: {}", longest_consecutive(nums));
}




/*
run:

Longest consecutive sequence length: 4

*/
  

 

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