Is Graph Bipartite.cpp

/*
Is Graph Bipartite?
===================

There is an undirected graph with n nodes, where each node is numbered between 0 and n - 1. You are given a 2D array graph, where graph[u] is an array of nodes that node u is adjacent to. More formally, for each v in graph[u], there is an undirected edge between node u and node v. The graph has the following properties:

There are no self-edges (graph[u] does not contain u).
There are no parallel edges (graph[u] does not contain duplicate values).
If v is in graph[u], then u is in graph[v] (the graph is undirected).
The graph may not be connected, meaning there may be two nodes u and v such that there is no path between them.
A graph is bipartite if the nodes can be partitioned into two independent sets A and B such that every edge in the graph connects a node in set A and a node in set B.

Return true if and only if it is bipartite.

Example 1:
Input: graph = [[1,2,3],[0,2],[0,1,3],[0,2]]
Output: false
Explanation: There is no way to partition the nodes into two independent sets such that every edge connects a node in one and a node in the other.

Example 2:
Input: graph = [[1,3],[0,2],[1,3],[0,2]]
Output: true
Explanation: We can partition the nodes into two sets: {0, 2} and {1, 3}.

Constraints:
graph.length == n
1 <= n <= 100
0 <= graph[u].length < n
0 <= graph[u][i] <= n - 1
graph[u] does not contain u.
All the values of graph[u] are unique.
If graph[u] contains v, then graph[v] contains u.
*/

class Solution
{
public:
  bool bfs(vector<vector<int>> &adj, int i, vector<int> &colors)
  {
    colors[i] = 1;
    queue<int> q;
    q.push(i);

    while (q.size())
    {
      auto curr = q.front();
      q.pop();
      int nc = 1 - colors[curr];

      for (auto &j : adj[curr])
      {
        if (colors[j] == -1)
        {
          colors[j] = nc;
          q.push(j);
        }
        else if (colors[j] == nc)
          continue;
        else
          return false;
      }
    }
    return true;
  }

  bool isBipartite(vector<vector<int>> &graph)
  {
    int n = graph.size();
    vector<int> colors(n, -1);
    for (int i = 0; i < n; ++i)
    {
      if (colors[i] == -1 && !bfs(graph, i, colors))
        return false;
    }

    return true;
  }
};