From 8ea07f51ad4ec1e8fb94e7bd2cb8df8d0b09ad38 Mon Sep 17 00:00:00 2001
From: Abdurrezzak Efe <abdurrezak.efe@ug.bilkent.edu.tr>
Date: Sat, 11 Nov 2017 18:06:58 +0200
Subject: [PATCH] Add files via upload

---
 21.PrimAlgorithm.cpp | 76 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 21.PrimAlgorithm.cpp

diff --git a/21.PrimAlgorithm.cpp b/21.PrimAlgorithm.cpp
new file mode 100644
index 0000000..ce7b800
--- /dev/null
+++ b/21.PrimAlgorithm.cpp
@@ -0,0 +1,76 @@
+/*
+ * This program constructs an undirected graph by taking edges and vertices from the user
+ * and sing Prim's Algorithm
+ * constructs a Minimum Spanning Tree
+ *
+ *      Coded by: Abdurrezak Efe
+ * */
+
+#include <iostream>
+#include <limits.h>
+using namespace std;
+
+const int V = 1000; //assumed number of vertices
+int edges[V+1][V+1] = {0}; //the graph itself
+
+int minKeyIndex(int keys[], bool inMST[], int v) //finding the minimum keyed vertex
+{
+    //finding the vertex with smallest key to add to MST
+    int minKey = INT_MAX, minIndex=-1;
+    for(int i=0; i<v; i++)
+        if(!inMST[i] && keys[i] < minKey)
+            minKey = keys[i], minIndex = i;
+
+    return minIndex;
+}
+
+void Prim( int v, int e)
+{
+    int keys[v];
+    int previous[v];
+    bool inMST[v];
+
+    for(int i=0;i<v;i++)
+        keys[i] = INT_MAX, inMST[i] = false;
+
+    keys[0] = 0;
+    previous[0] = -1;
+
+    int vertices = 0;
+    while(vertices < v-1) //there will be v vertices in MST
+    {
+
+        int u = minKeyIndex(keys, inMST, v);
+
+        //adding u to MST
+        inMST[u] = true;
+
+        //operating on u's neighbors to add the smallest
+        for(int i=0; i<v; i++)
+            if(edges[u][i] && !inMST[i] && edges[u][i] < keys[i])
+                previous[i] = u, keys[i] = edges[u][i];
+
+        vertices++;
+    }
+
+
+    //printing MST
+    int i = 1;
+    while(i<v)
+        cout << i << ", " <<  previous[i] << ", " << edges[i][previous[i]] << endl, i++;
+
+}
+
+// driver program to test above function
+int main()
+{
+    int v,e;
+    cin >> v >> e;
+
+    //constructing the graph
+    int x,y,w;
+    for(int i=0;i<e;i++)
+        cin >> x >> y >> w, edges[x][y] = edges[y][x] = w;
+
+    Prim(v, e);
+}
\ No newline at end of file