Merge pull request technojam#217 from gunjan543/pull-request-prims

Prims Algorithm for Minimum Spanning Tree

Prims.cpp

@@ -0,0 +1,71 @@
+#include<iostream>
+#include<vector>
+#include<queue>
+using namespace std;
+
+class Graph{
+	//adjacency list
+	vector<pair<int,int> >*l;
+	int V;
+
+public:
+	Graph(int n){
+		V=n;
+		l=new vector<pair<int,int>>[V];
+	}
+	void addEdge(int x,int y,int w){
+		l[x].push_back({y,w});
+		l[y].push_back({x,w});
+	}
+
+	int prim_mst(){
+    // Syntax to create a min heap for priority queue
+    // priority_queue <int, vector<int>, greater<int>> g = gq 		 
+    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> Q;
+    //make another array for mst set
+    //visited array that denotes whether a node has been included in MST or not
+    bool *vis=new bool[V]{0};
+    int ans=0;
+    //begin start from src node and push src node
+    Q.push({0,0});
+
+    while(!Q.empty()){
+    	//pick out the edge with min weight
+    	//because its min heap
+    	auto best=Q.top();
+    	Q.pop()
+
+    	int to=best.second;
+    	int weight=best.first;
+
+    	if(vis[to]){
+    		//discard edge , and continue
+    		continue;
+    	}
+    	//otherwise take the current edge
+    	ans+=weight;
+    	vis[to]=1;
+
+    	//add the new edges in the queue
+    	for(auto x:l[to]){
+    		if(vis[x.first]==0){
+    			Q.push({x.second,x.first});
+    		}
+    	}
+    }
+    return ans;
+
+	}
+};
+int main(){
+	int n,m;
+	cin>>n>>m;
+	Graph g(n);
+	for(int i=0;i<m;i++){
+		int x,y,w;
+		cin>>x>>y>>w;
+		g.addEdge(x-1,y-1,w);
+	}
+	cout<<g.prim_mst()<<endl;
+	return 0;
+}

quickSort.cpp

@@ -0,0 +1,42 @@
+//inspace algorithm
+//divide and conquer
+//N log N on avg case and N^2 worst case
+#include<iostream>
+using namespace std;
+
+int partition(int *a, int s, int e) {
+	int i = s - 1;
+	int j = s;
+	int pivot = a[e];
+	for (; j <= e - 1;) {
+		if (a[j] <= pivot) {
+			i = i + 1;
+			swap(a[i], a[j]);
+		}
+		j = j + 1;
+	}
+	swap(a[i + 1], a[e]);
+	return i + 1;
+
+}
+void quick_sort(int *arr, int s, int e) {
+	if (s >= e) {
+		return;
+	}
+//recursive case
+	int p = partition(arr, s, e);
+//left part
+	quick_sort(arr, s, p - 1);
+//right part
+	quick_sort(arr, p + 1, e);
+}
+
+int main() {
+	int arr[] = {2, 3, 8, 6, 1, 5, 4};
+	quick_sort(arr, 0, 6);
+
+	for (int i = 0; i <= 6; i++) {
+		cout << arr[i] << endl;
+	}
+	return 0;
+}