is_graph_bipartite2.cpp

#include <cassert>   
#include <cstdint>
#include <iostream>  
#include <queue>     
#include <vector>    

namespace graph {
bool checkBipartite(const std::vector<std::vector<int64_t>> &graph,
                    int64_t index, std::vector<int64_t> *visited) {
    std::queue<int64_t> q;  
    q.push(index);          
    (*visited)[index] = 1;  
    while (q.size()) {
        int64_t u = q.front();
        q.pop();
        for (uint64_t i = 0; i < graph[u].size(); i++) {
            int64_t v =
                graph[u][i];     
            if (!(*visited)[v])  
            {
                (*visited)[v] =
                    ((*visited)[u] == 1)
                        ? -1
                        : 1;  
                q.push(v);    
            } else if ((*visited)[v] ==
                       (*visited)[u])  
            {
                return false;
            }
        }
    }
    return true;  
}

bool isBipartite(const std::vector<std::vector<int64_t>> &graph) {
    std::vector<int64_t> visited(
        graph.size());  
 
    for (uint64_t i = 0; i < graph.size(); i++) {
        if (!visited[i])  
        {
            if (!checkBipartite(graph, i, &visited)) {
                return false;
            }
        }
    }
    return true;
}
}  // namespace graph

static void test() {
    std::vector<std::vector<int64_t>> graph = {{1, 3}, {0, 2}, {1, 3}, {0, 2}};
 
    assert(graph::isBipartite(graph) ==
           true);  
 
    std::vector<std::vector<int64_t>> graph_not_bipartite = {
        {1, 2, 3}, {0, 2}, {0, 1, 3}, {0, 2}};
 
    assert(graph::isBipartite(graph_not_bipartite) ==
           false);  
    std::cout << "All tests have successfully passed!\n";
}
int main() {
    test();  // run self-test implementations
    return 0;
}