q5

dijkstra.py

+#!/usr/bin/env python3
+
+def dijkstra(matrix, height, start):
+    distances = matrix[start-1]
+    visited = [start]
+    vertices = []
+    for i in range(height):
+        vertices.append(i)
+
+    while vertices:
+        min = float("Inf")
+        idx = findmin(height, distances, vertices)
+        
+        vertices.remove(idx)       
+
+        for i in range(height):
+            if i in vertices and matrix[0][i] and distances[i] > 0:
+                if distances[i-1] + matrix[0][i-1] < matrix[0][i]:
+                    distances[idx] = distances[i-1] + matrix[0][i]
+                    
+ 
+    print("Shortest distances from vertex %d to other vertices:\n" % start)
+    for i in range(height):
+         print("(%d,%d): %d" % (start, i+1, distances[i]))
+
+def findmin(height, distances, vertices):
+    min = float("Inf")
+    idx = 0
+
+    for i in range(height):
+        if i in vertices and distances[i] < min:
+            min = distances[i]
+            idx = i
+    
+    return idx
+
+if __name__=="__main__":
+    #adjacency matric from test 2, problem 6, as a 2D array
+    matrix = [[0, 4, 1, 5, 8, 10],
+              [4, 0, 2, 0, 0, 0],
+              [1, 2, 0, 0, 0, 0],
+              [5, 0, 0, 0, 2, 1],
+              [8, 0, 0, 2, 0, 1],
+              [10, 0, 0, 0, 1, 0]]
+   
+    print("Input Matrix:\n")
+    print("0  4  1  5  8  10\n4  0  2  0  0  0\n1  2  0  0  0  0\n5  0  0  0  2  0\n8  0  0  2  0  1\n10 0  0  0  1  0\n")
+
+    #gets height and width, without just assuming 6
+    height = len(matrix)
+    start = 1
+    dijkstra(matrix, height, start)