39 lines
1.0 KiB
Python
39 lines
1.0 KiB
Python
import sys
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from collections import defaultdict, deque, Counter
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from heapq import heappush, heappop, heapify
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from itertools import permutations, combinations
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from functools import lru_cache
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from typing import List, Optional
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def solve():
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# 입력 처리
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n = int(input())
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arr = list(map(int, input().split()))
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# 풀이 작성
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arr.sort()
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total = 0
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if(n==1 or n==2):
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print(total)
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else:
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for i in range(n):
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left = 0
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right = n-1
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goal = arr[i]
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while (left<right):
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if(arr[left]+arr[right]==goal):
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if(left!=i and right!=i):
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total+=1
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break
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elif (left==i):
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left+=1
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else:
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right-=1
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elif(arr[left]+arr[right]>goal):
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right-=1
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else:
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left+=1
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print(total)
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if __name__ == "__main__":
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solve()
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