dijkstra.cpp

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define sf scanf
#define pf printf
long long int binarySearch(long long int arr[],long long  int l, long long int r, long long int x)
{
  while (l <= r)
  {
    long long int m = l + (r-l)/2;

    if (arr[m] == x) return m;  // Check if x is present at mid

    if (arr[m] < x) l = m + 1; // If x greater, ignore left half

    else r = m - 1; // If x is smaller, ignore left half
  }
  return -1; // if we reach here, then element was not present
}
void merge(long long int arr[], long long int l, long long int m, long long int r)
{
    long long int i, j, k;
    long long int n1 = m - l + 1;
    long long int n2 =  r - m;

    /* create temp arrays */
   long long  int L[n1], R[n2];

    /* Copy data to temp arrays L[] and R[] */
    for(i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for(j = 0; j < n2; j++)
        R[j] = arr[m + 1+ j];

    /* Merge the temp arrays back into arr[l..r]*/
    i = 0;
    j = 0;
    k = l;
    while (i < n1 && j < n2)
    {
        if (L[i] <= R[j])
        {
            arr[k] = L[i];
            i++;
        }
        else
        {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    /* Copy the remaining elements of L[], if there are any */
    while (i < n1)
    {
        arr[k] = L[i];
        i++;
        k++;
    }

    /* Copy the remaining elements of R[], if there are any */
    while (j < n2)
    {
        arr[k] = R[j];
        j++;
        k++;
    }
}

/* l is for left index and r is right index of the sub-array
  of arr to be sorted */
void mergeSort(long long int arr[], long long int l, long long int r)
{
    if (l < r)
    {
        long long  int m = l+(r-l)/2;//Same as (l+r)/2, but avoids overflow for large l and h
        mergeSort(arr, l, m);
	    mergeSort(arr, m+1, r);
        merge(arr, l, m, r);
    }
}
void printArray(long long int A[], long long int size)
{
   long long  int i;
    for (i=0; i < size; i++)
        printf("%lld ", A[i]);
    printf("\n");
}
#define V 9
int minDistance(int dist[], bool sptSet[])
{
   int min = INT_MAX, min_index;
 
   for (int v = 0; v < V; v++)
     if (sptSet[v] == false && dist[v] <= min)
         min = dist[v], min_index = v;
 
   return min_index;
}
int printSolution(int dist[], int n)
{
   printf("Vertex   Distance from Source\n");
   for (int i = 0; i < V; i++)
      printf("%d \t\t %d\n", i, dist[i]);
}
void dijkstra(int graph[V][V], int src)
{
     int dist[V];
	 bool sptSet[V];
     for (int i = 0; i < V; i++)
        dist[i] = INT_MAX, sptSet[i] = false;
 dist[src] = 0;
 
     for (int count = 0; count < V-1; count++)
     {
       int u = minDistance(dist, sptSet);
       sptSet[u] = true;
       for (int v = 0; v < V; v++)
         if (!sptSet[v] && graph[u][v] && dist[u] != INT_MAX 
                                       && dist[u]+graph[u][v] < dist[v])
            dist[v] = dist[u] + graph[u][v];
     }
     printSolution(dist, V);
}
int main()
{
   int graph[V][V] = {{0, 4, 0, 0, 0, 0, 0, 8, 0},
                      {4, 0, 8, 0, 0, 0, 0, 11, 0},
                      {0, 8, 0, 7, 0, 4, 0, 0, 2},
                      {0, 0, 7, 0, 9, 14, 0, 0, 0},
                      {0, 0, 0, 9, 0, 10, 0, 0, 0},
                      {0, 0, 4, 0, 10, 0, 2, 0, 0},
                      {0, 0, 0, 14, 0, 2, 0, 1, 6},
                      {8, 11, 0, 0, 0, 0, 1, 0, 7},
                      {0, 0, 2, 0, 0, 0, 6, 7, 0}
                     };
 
    dijkstra(graph, 0);
 
    return 0;
}