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dijskstra.cpp
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dijskstra.cpp
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#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <stack>
#include <time.h>
#include <utility>
using namespace std;
vector<vector<pair<int, int>>> vertices;
vector<int> shortest_distance;
vector<bool> processed;
void find_shortest_path(int start)
{
const int num_vertices = vertices.size();
shortest_distance.resize(num_vertices);
processed.clear();
processed.resize(num_vertices, false);
processed[start] = true;
shortest_distance[start] = 0;
for (int iter = 2; iter <= num_vertices; iter++)
{
int min_step = INT_MAX;
int next_vertex = INT_MAX;
for (int i = 0; i < num_vertices; i++)
{
if (processed[i])
{
for (int j = 0; j < vertices[i].size(); j++)
{
if (!processed[vertices[i][j].first])
{
int curr_step = shortest_distance[i] + vertices[i][j].second;
if (curr_step < min_step)
{
min_step = curr_step;
next_vertex = vertices[i][j].first;
}
}
}
}
}
processed[next_vertex] = true;
shortest_distance[next_vertex] = min_step;
}
}
int main()
{
clock_t start = clock();
string line;
ifstream myfile("dijkstraData.txt");
if (myfile.is_open())
{
int curr_vertex = 0;
vector<pair<int,int>> temp_list;
vertices.push_back(temp_list);
pair<int, int> curr_pair;
while (getline(myfile, line))
{
int i = 0;
int current_int = 0;
const int line_size = line.size();
bool first = true;
while (i < line_size)
{
if (line[i] == '\t')
{
if (first)
{
curr_vertex = current_int - 1;
if (vertices.size() < curr_vertex + 1)
vertices.resize((curr_vertex + 1) * 2);
first = false;
}
else
{
curr_pair.second = current_int;
vertices[curr_vertex].push_back(curr_pair);
}
current_int = 0;
i++;
}
else if (line[i] == ',')
{
curr_pair.first = current_int - 1;
current_int = 0;
i++;
}
current_int = current_int * 10 + (line[i] - '0');
i++;
}
}
myfile.close();
vertices.resize(curr_vertex + 1);
}
else
{
cout << "Unable to open file";
}
clock_t end = clock();
cout << "File reading took " << double(end - start) / CLOCKS_PER_SEC << " seconds.\n";
start = clock();
find_shortest_path(0);
end = clock();
cout << "Dijkstra's algorithm took " << double(end - start) / CLOCKS_PER_SEC << " seconds.\n";
cout << "\nDistances to 7,37,59,82,99,115,133,165,188,197:\n";
cout << shortest_distance[6] << ",";
cout << shortest_distance[36] << ",";
cout << shortest_distance[58] << ",";
cout << shortest_distance[81] << ",";
cout << shortest_distance[98] << ",";
cout << shortest_distance[114] << ",";
cout << shortest_distance[132] << ",";
cout << shortest_distance[164] << ",";
cout << shortest_distance[187] << ",";
cout << shortest_distance[196] << "\n";
return 0;
}