Create Bellman Ford's algorithm.cpp

Author: nikolatechie

Bellman Ford's algorithm.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 n, m, src;
+vi dist;
+vector <tuple <int,int,int>> g;
+
+void bellmanFord()
+{
+    dist.assign(n, INF);
+    dist[src] = 0;
+
+    for (int t1 = 1; t1 < n; ++t1)
+    {
+        // use a bool variable to optimize the second for loop
+
+        for (int t2 = 0; t2 < m; ++t2)
+        {
+            int a = get<0>(g[t2]);
+            int b = get<1>(g[t2]);
+            int c = get<2>(g[t2]);
+            dist[b] = min(dist[b], dist[a]+c);
+            // if no improvements have been made, exit from these 2 for loops
+        }
+    }
+
+    for (int t1 = 0; t1 < m; ++t1)
+    {
+        int a = get<0>(g[t1]);
+        int b = get<1>(g[t1]);
+        int c = get<2>(g[t1]);
+
+        if (dist[b] > dist[a]+c)
+        {
+            cout << "Graph contains a negative cycle!\n";
+            return;
+        }
+    }
+
+    for (int t1 = 0; t1 < n; ++t1)
+        cout << dist[t1] << ' ';
+		
+    cout << '\n';
+}
+
+int main()
+{
+    ios_base::sync_with_stdio(0);
+    //cin.tie(0);
+
+    cin >> n >> m >> src;
+    g.resize(m);
+
+    for (int t1 = 0; t1 < m; ++t1)
+    {
+        int a, b, c;
+        cin >> a >> b >> c;
+        g[t1] = {a,b,c};
+    }
+
+    bellmanFord();
+
+
+
+    return 0;
+}