Create 1769.cpp

QUSTOJ/1769.cpp

@@ -0,0 +1,86 @@
+#include <iostream>
+using namespace std;
+const int maxnum = 10005;
+const int maxEdge= 50005;
+const int maxint = 107391822;
+
+// 边，
+typedef struct Edge{
+	int u, v;    // 起点，重点
+	int weight;  // 边的权值
+}Edge;
+
+Edge edge[maxEdge];     // 保存边的值
+int  dist[maxnum];     // 结点到源点最小距离
+
+int nodenum, edgenum, source;    // 结点数，边数，源点
+
+// 初始化图
+void init()
+{
+	// 输入结点数，边数，源点
+	cin >> nodenum >> edgenum ;
+	source=1;
+	for(int i=1; i<=nodenum; ++i)
+		dist[i] = maxint;
+	dist[source] = 0;
+	for(int i=1; i<=edgenum; i++)
+	{
+		cin >> edge[i].u >> edge[i].v >> edge[i].weight;
+		if(edge[i].u == source)          //注意这里设置初始情况
+			dist[edge[i].v] = edge[i].weight;
+
+        /*
+        /// Another
+        edge[i+1].u=edge[i].v;
+        edge[i+1].v=edge[i].u;
+        edge[i+1].weight=-edge[i].weight;
+
+        if(edge[i+1].u == source)          //注意这里设置初始情况
+			dist[edge[i+1].v] = edge[i+1].weight;
+        */
+	}
+}
+
+// 松弛计算
+void relax(int u, int v, int weight)
+{
+	if(dist[v] > dist[u] + weight)
+		dist[v] = dist[u] + weight;
+}
+
+bool Bellman_Ford()
+{
+	for(int i=1; i<=nodenum-1; ++i)
+		for(int j=1; j<=edgenum; ++j)
+			relax(edge[j].u, edge[j].v, edge[j].weight);
+	bool flag = 1;
+	// 判断是否有负环路
+	for(int i=1; i<=edgenum; ++i)
+		if(dist[edge[i].v] > dist[edge[i].u] + edge[i].weight)
+		{
+			flag = 0;
+			break;
+		}
+	return flag;
+}
+int main()
+{
+	//freopen("input3.txt", "r", stdin);
+    init();
+	if(Bellman_Ford())
+        //for(int i = 1 ;i <= nodenum; i++)
+			cout << dist[nodenum] << endl;
+    else
+        throw "WTF??";
+	return 0;
+}
+/*
+4 6
+1 2 -5
+2 3 -6
+1 3 -9
+2 4 -7
+3 4 -8
+1 4 6
+*/