create dev channel

zeta/py/completed/1326.py

@@ -0,0 +1,38 @@
+def solve(N, P, a, b):
+    a -= 1
+    b -= 1
+    D = []
+    D.append((a, 0))
+    visited = [2147483647] * N
+    visited[a] = 0
+    if b == a:
+        return 0
+    while D:
+        now, cost = D.pop(0)
+
+        if now == b:
+            return cost
+
+        from_now_on = now - P[now]
+        # - dir
+        while from_now_on >= 0:
+            if visited[from_now_on] > cost + 1:
+                visited[from_now_on] = cost + 1
+                D.append((from_now_on, cost + 1))
+            from_now_on -= P[now]
+        from_now_on = now + P[now]
+        # + dir
+        while from_now_on < N:
+            if visited[from_now_on] > cost + 1:
+                visited[from_now_on] = cost + 1
+                D.append((from_now_on, cost + 1))
+            from_now_on += P[now]
+
+    return -1
+
+
+if __name__ == "__main__":
+    N = int(input())
+    P = list(map(int, input().split()))
+    a, b = map(int, input().split())
+    print(solve(N, P, a, b))