init

7B.py

@@ -0,0 +1,57 @@
+import sys
+
+def f_lca(u, v_node):
+    if d[u] < d[v_node]:
+        u, v_node = v_node, u
+    diff = d[u] - d[v_node]
+    for k in range(18):
+        if (diff >> k) & 1:
+            u = up[u][k]
+    if u == v_node:
+        return u
+    for k in range(17, -1, -1):
+        if up[u][k] != up[v_node][k]:
+            u = up[u][k]
+            v_node = up[v_node][k]
+    return up[u][0]
+
+
+data = sys.stdin.read().split()
+n = int(data[0])
+v = [0] + [int(x) for x in data[1 : n + 1]]
+g = [[] for _ in range(n + 1)]
+idx = n + 1
+for _ in range(n - 1):
+    u, p_node = int(data[idx]), int(data[idx + 1])
+    g[u].append(p_node)
+    g[p_node].append(u)
+    idx += 2
+m = int(data[idx])
+idx += 1
+d = [0] * (n + 1)
+p = [0] * (n + 1)
+par = [0] * (n + 1)
+d[1] = 1
+p[1] = v[1]
+q = [1]
+for u in q:
+    for nv in g[u]:
+        if nv != par[u]:
+            par[nv] = u
+            d[nv] = d[u] + 1
+            p[nv] = p[u] + v[nv]
+            q.append(nv)
+up = [[0] * 18 for _ in range(n + 1)]
+for i in range(1, n + 1):
+    up[i][0] = par[i]
+for k in range(1, 18):
+    for i in range(1, n + 1):
+        up[i][k] = up[up[i][k - 1]][k - 1]
+out = []
+for _ in range(m):
+    x, y = int(data[idx]), int(data[idx + 1])
+    idx += 2
+    lca = f_lca(x, y)
+    ans = p[x] + p[y] - p[lca] - p[up[lca][0]]
+    out.append(str(ans))
+print("\n".join(out))