Rank transform of an array

Array Hash Table Sorting

70.8% acceptance

Feb 25, 2026

2374

114

Given an array of integers arr, replace each element with its rank. The rank represents how large the element is. The rank has the following rules: Rank is an integer starting from 1. The larger the element, the larger the rank. If two elements are equal, their rank must be the same. Rank should be as small as possible.

Solution

Rust

Time O(n log n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn array_rank_transform(arr: Vec<i32>) -> Vec<i32> {
    if arr.is_empty() { return vec![]; }
    let mut sorted = arr.clone();
    sorted.sort();
    sorted.dedup();
    let rank: std::collections::HashMap<i32, i32> = sorted.iter().enumerate()
      .map(|(i, &v)| (v, i as i32 + 1)).collect();
    arr.iter().map(|v| rank[v]).collect()
  }
}