added file for djikstars's in /greedy_approach

greedy_approach/djikstra.c

@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX 20
+#define INF 999
+
+int mat[MAX][MAX];
+int V;
+
+int dist[MAX];
+
+int q[MAX];
+int qp = 0;
+
+void enqueue (int v) {
+	q[qp++] = v;
+}
+
+int cf (void *a, void *b) {
+	int *x = (int *)a;
+	int *y = (int *)b;
+	return *y - *x;
+}
+
+int dequeue () {
+	qsort(q, qp, sizeof(int), cf);
+	return q[--qp];
+}
+
+int queue_has_something () {
+	return (qp > 0);
+}
+
+int visited[MAX];
+int vp = 0;
+
+void dijkstra (int s) {
+	dist[s] = 0;
+	int i;
+	for (i = 0; i < V; ++i) {
+		if (i != s) {
+			dist[i] = INF;
+		}
+		enqueue(i);
+	}
+	while (queue_has_something()) {
+		int u = dequeue();
+		visited[vp++] = u;
+		for (i = 0; i < V; ++i) {
+			if (mat[u][i]) {
+				if (dist[i] > dist[u] + mat[u][i]) {
+					dist[i] = dist[u] + mat[u][i];
+				}
+			}
+		}
+	}
+}
+
+int main(int argc, char const *argv[]) {
+
+	printf("Enter the number of vertices: ");
+	scanf(" %d", &V);
+	printf("Enter the adj matrix: ");
+	int i, j;
+	for (i = 0; i < V; ++i) {
+		for (j = 0; j < V; ++j) {
+			scanf(" %d", &mat[i][j]);
+		}
+	}
+	
+	dijkstra(0);
+
+	printf("\nNode\tDist\n");
+	for (i = 0; i < V; ++i) {
+		printf("%d\t%d\n", i, dist[i]);
+	}
+	
+	return  0;
+}