From 191e37ed2e098167c5dd704caefcf6d9aa73a014 Mon Sep 17 00:00:00 2001
From: Haidong Ji
Date: Sun, 19 Jul 2020 21:47:57 -0500
Subject: Bipartite check done!

---
 Sources/GraphAlgo.cpp | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/Sources/GraphAlgo.cpp b/Sources/GraphAlgo.cpp
index 7385763..71ed2c2 100644
--- a/Sources/GraphAlgo.cpp
+++ b/Sources/GraphAlgo.cpp
@@ -7,8 +7,14 @@
 using std::vector;
 using std::queue;
 
-void bfs(vector<vector<int>> &adj, int s, vector<int> &dist) {
+bool bfsBipartiteCheck(vector<vector<int>> &adj, int s) {
+	if (adj[s].size() == 0)
+		return true;
+
+	vector<int> dist(adj.size(), -1);
+	dist[s] = 0;
 	queue<int> vertexQ;
+
 	vertexQ.push(s);
 
 	while (!vertexQ.empty()) {
@@ -17,19 +23,23 @@ void bfs(vector<vector<int>> &adj, int s, vector<int> &dist) {
 		for (int i : adj[u]) {
 			if (dist[i] == -1) {
 				vertexQ.push(i);
-				dist[i] = dist[u] + 1;
-			}
+				if (dist[u] == 0)
+					dist[i] = 1;
+				if (dist[u] == 1)
+					dist[i] = 0;
+			} else if (dist[i] == dist[u])
+				return false;
 		}
 	}
+	return true;
 }
 
-int distance(vector<vector<int> > &adj, int s, int t) {
-	vector<int> dist(adj.size(), -1);
-	dist[s] = 0;
-
-	bfs(adj, s, dist);
-
-	return dist[t];
+int bipartite(vector<vector<int> > &adj) {
+	bool bipartiteCheckNodes = bfsBipartiteCheck(adj, 0);
+	if (bipartiteCheckNodes)
+		return 1;
+	else
+		return 0;
 }
 
 int main() {
@@ -42,10 +52,7 @@ int main() {
 		adj[x - 1].push_back(y - 1);
 		adj[y - 1].push_back(x - 1);
 	}
-	int s, t;
-	std::cin >> s >> t;
-	s--, t--;
-	std::cout << distance(adj, s, t);
+	std::cout << bipartite(adj);
 }
 
 //TEST(Acyclicity, ac1) {
-- 
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