Example 1: dijkstra algorithm c++
#include<bits/stdc++.h>
using namespace std;
int main()
{
int n = 9;
int mat[9][9] = { { 100,4,100,100,100,100,100,8,100},
{ 4,100,8,100,100,100,100,11,100},
{100,8,100,7,100,4,100,100,2},
{100,100,7,100,9,14,100,100,100},
{100,100,100,9,100,100,100,100,100},
{100,100,4,14,10,100,2,100,100},
{100,100,100,100,100,2,100,1,6},
{8,11,100,100,100,100,1,100,7},
{100,100,2,100,100,100,6,7,100}};
int src = 0;
int count = 1;
int path[n];
for(int i=0;i<n;i++)
path[i] = mat[src][i];
int visited[n] = {0};
visited[src] = 1;
while(count<n)
{
int minNode;
int minVal = 100;
for(int i=0;i<n;i++)
if(visited[i] == 0 && path[i]<minVal)
{
minVal = path[i];
minNode = i;
}
visited[minNode] = 1;
for(int i=0;i<n;i++)
if(visited[i] == 0)
path[i] = min(path[i],minVal+mat[minNode][i]);
count++;
}
path[src] = 0;
for(int i=0;i<n;i++)
cout<<src<<" -> "<<path[i]<<endl;
return(0);
}
Example 2: dijkstra's algorithm
# Providing the graph
n = int(input("Enter the number of vertices of the graph"))
# using adjacency matrix representation
vertices = [[0, 0, 1, 1, 0, 0, 0],
[0, 0, 1, 0, 0, 1, 0],
[1, 1, 0, 1, 1, 0, 0],
[1, 0, 1, 0, 0, 0, 1],
[0, 0, 1, 0, 0, 1, 0],
[0, 1, 0, 0, 1, 0, 1],
[0, 0, 0, 1, 0, 1, 0]]
edges = [[0, 0, 1, 2, 0, 0, 0],
[0, 0, 2, 0, 0, 3, 0],
[1, 2, 0, 1, 3, 0, 0],
[2, 0, 1, 0, 0, 0, 1],
[0, 0, 3, 0, 0, 2, 0],
[0, 3, 0, 0, 2, 0, 1],
[0, 0, 0, 1, 0, 1, 0]]
# Find which vertex is to be visited next
def to_be_visited():
global visited_and_distance
v = -10
for index in range(num_of_vertices):
if visited_and_distance[index][0] == 0 \
and (v < 0 or visited_and_distance[index][1] <=
visited_and_distance[v][1]):
v = index
return v
num_of_vertices = len(vertices[0])
visited_and_distance = [[0, 0]]
for i in range(num_of_vertices-1):
visited_and_distance.append([0, sys.maxsize])
for vertex in range(num_of_vertices):
# Find next vertex to be visited
to_visit = to_be_visited()
for neighbor_index in range(num_of_vertices):
# Updating new distances
if vertices[to_visit][neighbor_index] == 1 and
visited_and_distance[neighbor_index][0] == 0:
new_distance = visited_and_distance[to_visit][1]
+ edges[to_visit][neighbor_index]
if visited_and_distance[neighbor_index][1] > new_distance:
visited_and_distance[neighbor_index][1] = new_distance
visited_and_distance[to_visit][0] = 1
i = 0
# Printing the distance
for distance in visited_and_distance:
print("Distance of ", chr(ord('a') + i),
" from source vertex: ", distance[1])
i = i + 1