create dev channel

zeta/py/completed/1967.py

@@ -0,0 +1,40 @@
+def solve(N, E):
+    D = []
+    D.append((0, 1, 0))
+    finals = []
+    while D:
+        before, header, distance = D.pop(0)
+        nexts = E[header]
+        cnt = 0
+        for s in nexts:
+            if s[0] != before:
+                D.append((header, s[0], distance + s[1]))
+                cnt += 1
+        if cnt == 0:
+            finals.append((header, distance))
+
+    D = []
+    s1 = max(finals, key=lambda x: x[1])
+    D.append((0, s1[0], 0))
+    finals = []
+    while D:
+        before, header, distance = D.pop(0)
+        nexts = E[header]
+        cnt = 0
+        for s in nexts:
+            if s[0] != before:
+                D.append((header, s[0], distance + s[1]))
+                cnt += 1
+        if cnt == 0:
+            finals.append((header, distance))
+
+    return max(finals, key=lambda x: x[1])[1]
+
+
+if __name__ == '__main__':
+    N: int = int(input())
+    E = [[] for _ in range(N + 1)]
+    for a, b, v in [map(int, input().split()) for _ in range(N - 1)]:
+        E[a].append((b, v))
+        E[b].append((a, v))
+    print(solve(N, E))