Added dijkstra algorithm implementation in c++

graph/c++/dijkstra.cpp

@@ -0,0 +1,38 @@
+#include <bits/stdc++.h>
+#include <iostream>
+using namespace std;
+
+#define fst first
+#define snd second
+#define pb(a) push_back(a)
+#define mp(a, b) make_pair(a, b)
+typedef long long ll;
+
+const int N = 1e5 + 5;
+int v, y, cost, best[N];
+vector<pair<int, int>> graph[N];
+
+void dijkstra(int x) {
+	memset(best, -1, sizeof best);
+	priority_queue<pair<int, int>> queue;
+	best[x] = 0; // First node.
+	queue.push({x, -best[x]}); // Now it's {x, 0}.
+
+	while(queue.size()){ // While it's not empty.
+		y = queue.top().fst; // The node we're now.
+		cost = -queue.top().snd; // The cost to that node.
+		queue.pop(); // We don't need that node anymore.
+
+		if(cost > best[y]) continue;
+		for(int i = 0; i < graph[x].size(); i++){ // For every neighbour of x...
+			v = graph[x][i].fst; // Get the node.
+			cost = graph[x][i].snd; // Get it's cost.
+
+			// If it's unvisited, or we found a better path...
+			if(best[v] < 0 or best[y] + cost < best[v]){
+				best[v] = best[y] + cost; // Change the cost.
+				queue.push(mp(v, -best[v])); // Push that node to the queue to visit it's neighbours.
+			}
+		}
+	}
+}

graph/c++/kruskal.cpp

@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define fst first
+#define snd second
+#define pb(a) push_back(a)
+#define mp(a, b) make_pair(a, b)
+#define ll long long
+const int N = 1000;
+vector<pair<ll,pair<ll,ll>>> g; // Graph (cost, (x, y))
+ll n, m, a, b, c, mst_weight, mst_vertex, mst_edges, ancestors[N];
+
+void set_fathers(){
+	for(ll i = 0; i < N; i++){
+		ancestors[i] = i;
+	}
+}
+
+ll father(ll x){
+	if(ancestors[x] == x) return x;
+	else return father(ancestors[x]);
+}
+
+void unite(ll a, ll b){
+	ll father_a = father(a);
+	ll father_b = father(b);
+	ancestors[father_a] = father_b;
+}
+
+void kruskal(){
+	set_fathers();
+	sort(g.begin(), g.end());
+
+	while(mst_vertex < n - 1 or mst_edges < m){
+		a = g[mst_edges].snd.fst;
+		b = g[mst_edges].snd.snd;
+		c = g[mst_edges].fst;
+		if(father(a) != father(b)){
+			unite(a, b);
+			mst_weight += c;
+			mst_vertex++;
+		}
+		mst_edges++;
+	}
+}
+
+int main(){
+	cin >> n >> m;
+	for(ll i = 0; i < m; i++){
+		cin >> a >> b >> c;
+		g.pb(mp(c, mp(a,b)));
+	}
+	kruskal();
+	return 0;
+}