760. Find Anagram Mappings

Given two lists Aand B, and B is an anagram of A. B is an anagram of A means B is made by randomizing the order of the elements in A.

We want to find an index mapping P, from A to B. A mapping P[i] = j means the ith element in A appears in B at index j.

These lists A and B may contain duplicates. If there are multiple answers, output any of them.

For example, given

A = [12, 28, 46, 32, 50]
B = [50, 12, 32, 46, 28]

We should return
[1, 4, 3, 2, 0]
as P[0] = 1 because the 0th element of A appears at B[1], and P[1] = 4 because the 1st element of A appears at B[4], and so on.

Note:

  1. A, B have equal lengths in range [1, 100].
  2. A[i], B[i] are integers in range [0, 10^5].

Rust Solution

struct Solution;

use std::collections::HashMap;

impl Solution {
    fn anagram_mappings(a: Vec<i32>, b: Vec<i32>) -> Vec<i32> {
        let mut hs: HashMap<i32, Vec<i32>> = HashMap::new();
        let n = a.len();
        for (i, &x) in b.iter().enumerate() {
            let indexes = hs.entry(x).or_default();
            indexes.push(i as i32);
        }
        let mut res: Vec<i32> = vec![0; n];
        for (i, &x) in a.iter().enumerate() {
            let indexes = hs.entry(x).or_default();
            res[i] = indexes.pop().unwrap();
        }
        res
    }
}

#[test]
fn test() {
    let a = vec![12, 28, 46, 32, 50];
    let b = vec![50, 12, 32, 46, 28];
    let res = vec![1, 4, 3, 2, 0];
    assert_eq!(Solution::anagram_mappings(a, b), res);
}

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