CSP 5-10 树的优化

CSP-Training/5/10-tree.cpp

@@ -0,0 +1,52 @@
+//树的优化 | CF682C Alyona and the Tree
+#include <cstdio>
+#include <iostream>
+using namespace std;
+int head[100001], nxt[100000], to[100000], val[100001], weight[100000];
+int n, preserveCount;
+void dfs(int currPos, int dist);
+void insert(const int &source, const int &dest, const int &wt);
+int main()
+{
+    int parentTemp, weightTemp;
+    scanf("%d", &n);
+    for (int i = 1; i <= n; i++)
+    {
+        scanf("%d", &val[i]);
+    }
+    for (int i = 1; i < n; i++) //从第2号结点开始输入父节点和边权
+    {
+        scanf("%d %d", &parentTemp, &weightTemp);
+        insert(parentTemp, i + 1, weightTemp); //只需要加一条，这个是有向的
+    }
+    dfs(1, 0);
+    printf("%d", n - preserveCount);
+    return 0;
+}
+void dfs(int currPos, int dist)
+{
+    if (dist > val[currPos])
+    {
+        return;
+    }
+    preserveCount++;
+    for (int i = head[currPos]; i != 0; i = nxt[i])
+    {
+        if (dist > 0)
+        {
+            dfs(to[i], dist + weight[i]);
+        }
+        else
+        {
+            dfs(to[i], weight[i]);
+        }
+    }
+    return;
+}
+void insert(const int &source, const int &dest, const int &wt)
+{
+    nxt[dest - 1] = head[source];
+    head[source] = dest - 1;
+    to[dest - 1] = dest;
+    weight[dest - 1] = wt;
+}