1042. Flower Planting With No Adjacent

You have n gardens, labeled from 1 to n, and an array paths where paths[i] = [xi, yi] describes a bidirectional path between garden xi to garden yi. In each garden, you want to plant one of 4 types of flowers.

All gardens have at most 3 paths coming into or leaving it.

Your task is to choose a flower type for each garden such that, for any two gardens connected by a path, they have different types of flowers.

Return any such a choice as an array answer, where answer[i] is the type of flower planted in the (i+1)th garden. The flower types are denoted 1, 2, 3, or 4. It is guaranteed an answer exists.

 

Example 1:

Input: n = 3, paths = [[1,2],[2,3],[3,1]]
Output: [1,2,3]
Explanation:
Gardens 1 and 2 have different types.
Gardens 2 and 3 have different types.
Gardens 3 and 1 have different types.
Hence, [1,2,3] is a valid answer. Other valid answers include [1,2,4], [1,4,2], and [3,2,1].

Example 2:

Input: n = 4, paths = [[1,2],[3,4]]
Output: [1,2,1,2]

Example 3:

Input: n = 4, paths = [[1,2],[2,3],[3,4],[4,1],[1,3],[2,4]]
Output: [1,2,3,4]

 

Constraints:

  • 1 <= n <= 104
  • 0 <= paths.length <= 2 * 104
  • paths[i].length == 2
  • 1 <= xi, yi <= n
  • xi != yi
  • Every garden has at most 3 paths coming into or leaving it.

Rust Solution

struct Solution;

impl Solution {
    fn garden_no_adj(n: i32, paths: Vec<Vec<i32>>) -> Vec<i32> {
        let n = n as usize;
        let mut g: Vec<Vec<usize>> = vec![vec![]; n];
        for path in paths {
            let u = (path[0] - 1) as usize;
            let v = (path[1] - 1) as usize;
            g[u].push(v);
            g[v].push(u);
        }
        let mut colors: Vec<i32> = vec![0; n];
        for i in 0..n {
            let mut used: Vec<bool> = vec![false; 5];
            for &j in &g[i] {
                used[colors[j] as usize] = true;
            }
            for c in 1..5 {
                if !used[c] {
                    colors[i] = c as i32;
                    break;
                }
            }
        }
        colors
    }
}

#[test]
fn test() {
    let n = 3;
    let paths: Vec<Vec<i32>> = vec_vec_i32![[1, 2], [2, 3], [3, 1]];
    let res = vec![1, 2, 3];
    assert_eq!(Solution::garden_no_adj(n, paths), res);
    let n = 4;
    let paths: Vec<Vec<i32>> = vec_vec_i32![[1, 2], [3, 4]];
    let res = vec![1, 2, 1, 2];
    assert_eq!(Solution::garden_no_adj(n, paths), res);
    let n = 4;
    let paths: Vec<Vec<i32>> = vec_vec_i32![[1, 2], [2, 3], [3, 4], [4, 1], [1, 3], [2, 4]];
    let res = vec![1, 2, 3, 4];
    assert_eq!(Solution::garden_no_adj(n, paths), res);
}

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