Minimum Spanning Tree: Prim's Algorithm

Author: Faisal786111

Graph/Minimum Spanning Tree/Prim's Algorithm/main.c

@@ -0,0 +1,85 @@
+#include <stdio.h>
+
+#define I 32767
+
+// Algorithm:
+/**
+ * 1. First select vertices having minimum edge cost from cost matrix
+ * 2. Select the adjacent Vertices having minimum edge cost
+ */
+
+// Initialization 
+int cost[8][8] = {
+    {I, I, I, I, I, I, I, I},
+    {I, I, 25, I, I, I, 5, I},
+    {I, 25, I, 12, I, I, I, 10},
+    {I, I, 12, I, 8, I, I, I},
+    {I, I, I, 8, I, 16, I, 14},
+    {I, I, I, I, 16, I, 20, 18},
+    {I, 5, I, I, I, 20, I, I},
+    {I, I, 10, I, 14, 18, I, I}
+};
+
+// Initialize as Infinity
+int near[8] = {I, I, I, I, I, I, I, I};
+
+// n-> nodes , n-1 -> edges(6)
+int t[2][6];
+
+int main(){
+    int i, j, u, v, k,min = I, n=7, sum=0;
+
+    // Initial work
+    // Find minimum edge from Cost matrix(upper triangular)
+    for(i = 1; i<=n;i++){
+        for(j = i; j<=n ;j++){
+            if(cost[i][j] < min){
+                min = cost[i][j];
+                u = i; v = j;
+            }
+        }
+    }
+
+    near[u] = near[v] = 0;
+    t[0][0] = u; t[1][0] = v;
+    sum += min;
+
+    // Identify near vertex having minium edge and connected by the selected edge 
+      for (i = 1; i <= n; i++) {
+        if (near[i] != 0) { 
+            near[i] = (cost[i][u] < cost[i][v]) ? u : v;
+        }
+    }
+
+    // Repeatetion work 
+    for(i=1; i<n-1 ;i++){
+        min = I;
+        // Identify min edge from near array 
+        for(j=1; j<=n; j++){
+            if(near[j]!=0 && cost[j][near[j]]<min){
+                min = cost[j][near[j]];
+                k = j;
+            }
+        }
+
+        // update Spanning tree and near array too
+        t[0][i] = k; t[1][i] = near[k];
+        near[k] = 0;
+        sum += min;
+
+        // Identify near vertex having minium edge and connected by the selected edge
+        for(j=1; j<=n; j++){
+            if(near[j]!=0 && cost[j][k] < cost[j][near[j]]){
+                near[j] = k;
+            }
+        }
+    }
+
+    for(i=0; i<n-1;i++){
+        printf("(%d, %d),",t[0][i],t[1][i]);
+    }
+
+    printf("\nTotal cost: %d",sum);
+
+    return 0;
+}