Add BellmanFord Algorithm for CPP

CPP/BellmanFord.cpp

@@ -1,43 +1,61 @@
-//saru95
-#include <fstream>
-#include <iostream>
-#include <string>
-#include <cstring>
-#include <complex>
-#include <math.h>
-#include <utility>
-#include <cmath>
-#include <set>
-#include <vector>
-#include <map>
-#include <cctype>
-#include <queue>
-#include <stdio.h>
-#include <cstdio>
-#include <stack>
-#include <algorithm>
-#include <list>
-#include <ctime>
-#include <time.h>
-#include <stdlib.h>
-#include <numeric>
-#include <memory.h>
-
-#define all(a) (a).begin(),(a).end()
-#define gcd __gcd
-#define bitcount __builtin_popcount
+#include <algorithm>
+#include <iostream>
+
+#define INF 100000000
 
 using namespace std;
-
-typedef std::vector<int> vi;
-typedef std::vector<std::string> vs;
-typedef std::pair<int, int> pii;
-typedef std::set<int> si;
-typedef std::map<std::string, int> msi;
-
-
+
+typedef struct edge {
+	int u, v, w;
+} edge;
+
+vector<edge> edges;
+vector<int> dis;
+bool has_negative_cycle;
+int n_nodes;
+
+void bellmanford(int src) {
+	dis[src] = 0;
+	has_negative_cycle = false;
+	edge e;
+	for(int i = 1;i < n_nodes;i++) {
+		for(vector<edge>::iterator it = edges.begin();it != edges.end();it++) {
+			e = *it;
+			if(dis[e.u] != INF) {
+				dis[e.v] = min(dis[e.u] + e.w, dis[e.v]);
+			}
+		}
+	}
+	// detect negative cycle
+	for(vector<edge>::iterator it = edges.begin();it != edges.end() && !has_negative_cycle;it++) {
+		e = *it;
+		if(dis[e.u] != INF && dis[e.u] + e.w < dis[e.v]) {
+			has_negative_cycle = true;
+		}
+	}
+}
 
 int main(int argc, char const *argv[]) {
-
-  return 0;
+	int n_edges, u, v, w;
+	cin >> n_nodes;
+	dis.assign(n_nodes, INF);
+	cin >> n_edges;
+	while(n_edges--) {
+		cin >> u >> v >> w;
+		edges.push_back({u, v, w});
+	}
+	// input source node
+	cin >> u;
+	bellmanford(u);
+	if(has_negative_cycle) {
+		cout << "Negative cycle detected" << endl;
+	}
+	else {
+		cout << "No negative cycle detected" << endl;
+		for(int i = 0;i < n_nodes;i++) {
+			cout << i << ": " << dis[i] << endl;
+		}
+	}
+
+	return 0;
 }