Create Dijkstra's algorithm - SSSP.cpp

Author: nikolatechie

Dijkstra's algorithm - SSSP.cpp

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+#include <bits/stdc++.h>
+#include <ext/rope>
+using namespace std;
+using namespace __gnu_cxx;
+
+using ld = long double;
+using llint = long long;
+using ullint = unsigned long long;
+using pii = pair <int,int>;
+using pcc = pair <char,char>;
+using pss = pair <string,string>;
+using vi = vector <int>;
+using vb = vector <bool>;
+using vii = vi::iterator;
+
+#define INF (1<<30)
+#define MOD 1000000007
+#define mp make_pair
+#define mt make_tuple
+#define all(c) c.begin(), c.end()
+#define ms(name,val) memset(name, val, sizeof name)
+#define np nullptr
+
+
+int main()
+{
+    ios_base::sync_with_stdio(0);
+    //cin.tie(0);
+
+    int n, m, s;
+    cin >> n >> m >> s;
+    vector <vector <pii>> g(n);
+
+    for (int t1 = 0; t1 < m; ++t1)
+    {
+        int a, b, c;
+        cin >> a >> b >> c;
+        g[a].push_back({b,c});
+        g[b].push_back({a,c});
+    }
+
+    set <pii> S; // dist, node
+    S.insert({0, s});
+
+    for (int t1 = 0; t1 < n; ++t1)
+        if (t1 != s) S.insert({INF, t1});
+
+    vb vis(n, 0);
+    vi p(n, -1), dist(n, INF);
+    dist[s] = 0;
+
+    for (int t1 = 0; t1 < n-1; ++t1)
+    {
+        int node = S.begin()->second;
+        int ndist = S.begin()->first;
+        S.erase(S.begin());
+        vis[node] = 1;
+
+        for (int t2 = 0; t2 < g[node].size(); ++t2)
+        {
+            int x = g[node][t2].first;
+            int y = g[node][t2].second;
+            if (vis[x]) continue;
+
+            if (dist[x] > ndist+y)
+            {
+                S.erase({dist[x], x});
+                dist[x] = ndist+y;
+                S.insert({dist[x], x});
+                p[x] = node; // for finding the path
+            }
+        }
+    }
+
+    cout << '\n';
+
+    for (int t1 = 0; t1 < n; ++t1)
+    {
+        cout << dist[t1] << " ->  ";
+        int node = t1;
+
+        while (node != -1)
+        {
+            cout << node << ' ';
+            node = p[node];
+        }
+
+        cout << '\n';
+    }
+
+
+    return 0;
+}