Create BellmanFord.cpp

Bellman Ford : Minimum Spanning Tree Algorithm

CPP/BellmanFord.cpp

@@ -0,0 +1,55 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define ll long long int
+#define pb push_back
+
+// for 1 based indexing
+
+map<pair<int, int> , int > mpx;
+vector<int> bellman_ford(vector<vector<int> > adj, int src, int n)
+{
+	vector<int> dist(n + 1, INT_MAX);
+	dist[src] = 0;
+	for (int i = 0; i < n - 1; i++) // Relaxation n-1 times.
+	{
+		for (auto it = mpx.begin(); it != mpx.end(); it++)
+		{
+			int from = it->first.first, to = it->first.second;
+			int weight = mpx[ {from, to}];
+			if (dist[from] != INT_MAX && (dist[to] > dist[from] + weight)) // 1st condition to check overflow
+				dist[to] = dist[from] + weight;
+		}
+
+	}
+	// Check for negative cycle;
+	for (auto it = mpx.begin(); it != mpx.end(); it++)
+	{
+		int from = it->first.first, to = it->first.second;
+		int weight = mpx[ {from, to}];
+		if (dist[to] > dist[from] + weight)
+		{
+			cout << "Negative Cycle Present" << endl;
+			exit(0);
+		}
+	}
+	return dist;
+}
+
+int main()
+{
+	int n, m, src;
+	cin >> n >> m;
+	vector<vector<int> > adj(n + 1);
+	for (int i = 0; i < m; i++) {
+		int a, b, c;
+		cin >> a >> b >> c;
+		mpx[ {a, b}] = c;
+		adj[a].pb(b);
+	}
+	//cout << "Enter Source: " << endl;
+	src = 0;
+	vector<int> res = bellman_ford(adj, src, n);
+	for (int i = 0; i < res.size(); i++)
+		cout << res[i] << " ";
+
+}