Merge pull request #147 from vmmc2/master

Implement Dijkstra path-finding (adjacency list, w/ small local optimizations) in C++

graphs/Dijkstra.cpp

@@ -0,0 +1,36 @@
+#include <bits/stdc++.h>
+#define INF 9999999
+#define MAXN 100000
+
+using namespace std;
+
+typedef pair<int,int> pii;
+vector<pii> adjlist[MAXN];
+int distancias[MAXN];
+
+void Dijkstra(int s){
+    for(int i = 0; i < MAXN; i++){
+        distancias[i] = INF;
+    }
+    distancias[s] = 0;
+    priority_queue< pii, vector<pii>, greater<pii> >heap;
+    heap.push({0,s});
+    while(!heap.empty()){
+        int dist, atualvertex;
+        dist = heap.top().first;
+        atualvertex = heap.top().second;
+        heap.pop();
+        if(dist > distancias[atualvertex]){
+            continue;
+        }
+        for(int i = 0; i < (int)adjlist[atualvertex].size(); i++){
+            int dist2, proxvertex;
+            dist2 = adjlist[atualvertex][i].first;
+            proxvertex = adjlist[atualvertex][i].second;
+            if(distancias[proxvertex] > distancias[atualvertex] + dist2){
+                distancias[proxvertex] = distancias[atualvertex] + dist2;
+                heap.push({distancias[proxvertex], proxvertex});
+            }
+        }
+    }
+}