'commit'

TangDou/AcWing/SystemOfDifferenceConstraints/P1339_BellmanFord_Ljb.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int INF = 0x3f3f3f3f;
+const int N = 2510;          //结点数
+const int M = 6200 * 2 + 10; //边数
+
+//邻接表
+int e[M], h[N], idx, w[M], ne[M];
+void add(int a, int b, int c) {
+    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
+}
+
+int n, m; // n个结点，m条边
+int s, t; //起点，终点
+int d[N]; //距离数组
+
+void bellman_ford(int start) {
+    memset(d, 0x3f, sizeof d);
+    d[start] = 0;
+    int T = n - 1;                              //常规的Bellman_Ford是执行n-1次
+    while (T--) {                               //松驰n-1次
+        for (int k = 1; k <= n; k++)            //枚举1~n节点
+            for (int i = h[k]; ~i; i = ne[i]) { //二层循环枚举每个节点的出边
+                int j = e[i];
+                d[j] = min(d[j], d[k] + w[i]);
+            }
+    }
+}
+
+int main() {
+    memset(h, -1, sizeof h);
+    cin >> n >> m >> s >> t;
+    for (int i = 0; i < m; i++) {
+        int a, b, c;
+        cin >> a >> b >> c;
+        add(a, b, c), add(b, a, c);
+    }
+    bellman_ford(s);
+    cout << d[t] << endl;
+    return 0;
+}