Formatted question description: https://leetcode.ca/all/1042.html

# 1042. Flower Planting With No Adjacent (Easy)

You have `N`

gardens, labelled `1`

to `N`

. In each garden, you want to plant one of 4 types of flowers.

`paths[i] = [x, y]`

describes the existence of a bidirectional path from garden `x`

to garden `y`

.

Also, there is no garden that has more than 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]

**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]

**Note:**

`1 <= N <= 10000`

`0 <= paths.size <= 20000`

- No garden has 4 or more paths coming into or leaving it.
- It is guaranteed an answer exists.

**Related Topics**:

Graph

## Solution 1.

```
// OJ: https://leetcode.com/problems/flower-planting-with-no-adjacent/
// Time: O(N)
// Space: O(N)
class Solution {
public:
vector<int> gardenNoAdj(int N, vector<vector<int>>& paths) {
vector<vector<int>> G(N);
for (auto & e : paths) {
G[e[0] - 1].push_back(e[1] - 1);
G[e[1] - 1].push_back(e[0] - 1);
}
vector<int> ans(N);
for (int i = 0; i < N; ++i) {
int color[5] = {};
for (int j : G[i]) color[ans[j]] = 1;
for (int j = 4; j > 0; --j) {
if (color[j]) continue;
ans[i] = j;
break;
}
}
return ans;
}
};
```

Java

```
class Solution {
public int[] gardenNoAdj(int N, int[][] paths) {
int[] flowers = new int[N];
Map<Integer, List<Integer>> adjacentMap = new HashMap<Integer, List<Integer>>();
for (int[] path : paths) {
int garden1 = path[0] - 1, garden2 = path[1] - 1;
List<Integer> pathList1 = adjacentMap.getOrDefault(garden1, new ArrayList<Integer>());
pathList1.add(garden2);
adjacentMap.put(garden1, pathList1);
List<Integer> pathList2 = adjacentMap.getOrDefault(garden2, new ArrayList<Integer>());
pathList2.add(garden1);
adjacentMap.put(garden2, pathList2);
}
flowers[0] = 1;
for (int i = 1; i < N; i++) {
List<Integer> adjacent = adjacentMap.getOrDefault(i, new ArrayList<Integer>());
boolean[] used = new boolean[5];
for (int garden : adjacent) {
int flower = flowers[garden];
if (flower > 0)
used[flower] = true;
}
for (int j = 1; j < 5; j++) {
if (!used[j]) {
flowers[i] = j;
break;
}
}
}
return flowers;
}
}
```