Create FirstSearch.cpp

Best first search implemented in c++.

C++/FirstSearch.cpp

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+// C++ program to implement Best First Search using priority
+// queue
+#include <bits/stdc++.h>
+using namespace std;
+typedef pair<int, int> pi;
+
+vector<vector<pi> > graph;
+
+// Function for adding edges to graph
+void addedge(int x, int y, int cost)
+{
+	graph[x].push_back(make_pair(cost, y));
+	graph[y].push_back(make_pair(cost, x));
+}
+
+// Function For Implementing Best First Search
+// Gives output path having lowest cost
+void best_first_search(int source, int target, int n)
+{
+	vector<bool> visited(n, false);
+	// MIN HEAP priority queue
+	priority_queue<pi, vector<pi>, greater<pi> > pq;
+	// sorting in pq gets done by first value of pair
+	pq.push(make_pair(0, source));
+	int s = source;
+	visited[s] = true;
+	while (!pq.empty()) {
+		int x = pq.top().second;
+		// Displaying the path having lowest cost
+		cout << x << " ";
+		pq.pop();
+		if (x == target)
+			break;
+
+		for (int i = 0; i < graph[x].size(); i++) {
+			if (!visited[graph[x][i].second]) {
+				visited[graph[x][i].second] = true;
+				pq.push(make_pair(graph[x][i].first,graph[x][i].second));
+			}
+		}
+	}
+}
+
+// Driver code to test above methods
+int main()
+{
+	// No. of Nodes
+	int v = 14;
+	graph.resize(v);
+
+	// The nodes shown in above example(by alphabets) are
+	// implemented using integers addedge(x,y,cost);
+	addedge(0, 1, 3);
+	addedge(0, 2, 6);
+	addedge(0, 3, 5);
+	addedge(1, 4, 9);
+	addedge(1, 5, 8);
+	addedge(2, 6, 12);
+	addedge(2, 7, 14);
+	addedge(3, 8, 7);
+	addedge(8, 9, 5);
+	addedge(8, 10, 6);
+	addedge(9, 11, 1);
+	addedge(9, 12, 10);
+	addedge(9, 13, 2);
+
+	int source = 0;
+	int target = 9;
+
+	// Function call
+	best_first_search(source, target, v);
+
+	return 0;
+}