AOJ ALDS1_4_B Binary Search
備忘録
問題
http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_4_B&lang=ja
回答
import sys, os, math, bisect, itertools, collections, heapq, queue # from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall from decimal import Decimal from collections import defaultdict, deque import copy sys.setrecursionlimit(10000000) ii = lambda: int(sys.stdin.buffer.readline().rstrip()) il = lambda: list(map(int, sys.stdin.buffer.readline().split())) fl = lambda: list(map(float, sys.stdin.buffer.readline().split())) iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] iss = lambda: sys.stdin.buffer.readline().decode().rstrip() sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] lcm = lambda x, y: (x * y) // math.gcd(x, y) MOD = 10 ** 9 + 7 MAX = float('inf') def binary_search(S, target, left, right): while left < right: middle = (left + right) // 2 if S[middle] > target: right = middle elif S[middle] < target: left = middle + 1 elif S[middle] == target: return middle else: return -1 def main(): if os.getenv("LOCAL"): sys.stdin = open("input.txt", "r") N = ii() S = il() Q = ii() T = il() ret = 0 for t in T: if binary_search(S, t, 0, N) > 0: ret += 1 print(ret) if __name__ == '__main__': main()
考え方
螺旋本より、二分探索の問題。
通常の探索ではO(nq)
になるため、二分探索を用いて
同一の整数の有無を判定する。
が、pythonであればset
を使えば回答できる。。
setを使用した例
import sys, os, math, bisect, itertools, collections, heapq, queue # from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall from decimal import Decimal from collections import defaultdict, deque import copy sys.setrecursionlimit(10000000) ii = lambda: int(sys.stdin.buffer.readline().rstrip()) il = lambda: list(map(int, sys.stdin.buffer.readline().split())) fl = lambda: list(map(float, sys.stdin.buffer.readline().split())) iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] iss = lambda: sys.stdin.buffer.readline().decode().rstrip() sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] lcm = lambda x, y: (x * y) // math.gcd(x, y) MOD = 10 ** 9 + 7 MAX = float('inf') def main(): if os.getenv("LOCAL"): sys.stdin = open("input.txt", "r") N = ii() S = set(il()) Q = ii() T = set(il()) ret = 0 for t in T: if t in S: ret += 1 print(ret) if __name__ == '__main__': main()