'commit'

TangDou/AcWing/P1339_SPFA.cpp

@@ -0,0 +1,58 @@
+#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
+
+int n, m; // n个结点，m条边
+int s, t; //起点，终点
+
+//邻接表
+int h[N], e[M], w[M], ne[M], idx;
+void add(int a, int b, int c) {
+    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
+}
+int d[N];   //最短距离数组
+bool st[N]; //是不是进过队列
+
+// spfa模板
+void spfa(int start) {
+    //将所有距离初始化为无穷大
+    memset(d, 0x3f, sizeof d);
+
+    //出发点的距离清零
+    d[start] = 0;
+    queue<int> q;
+    q.push(start);    //出发点入队列
+    st[start] = true; //出发点标识已使用
+
+    while (q.size()) {
+        int t = q.front();
+        q.pop();
+        st[t] = false;
+        for (int i = h[t]; ~i; i = ne[i]) {
+            int j = e[i];
+            if (d[j] > d[t] + w[i]) {
+                d[j] = d[t] + w[i];
+                if (!st[j]) {
+                    st[j] = true;
+                    q.push(j);
+                }
+            }
+        }
+    }
+}
+
+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);
+    }
+    spfa(s);
+    cout << d[t] << endl;
+    return 0;
+}