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문제요약 만들 수 있는 (0, 1) 쌍의 개수를 구하시오. 풀이 배열을 순회하면서 0의 개수를 누적해서 더하고, 1을 만나면 누적된 0의 개수를 더한다. 코드 시간복잡도 O(N) public static int solution(int[] A) { int pairs = 0; int count_zero = 0; for (int n : A) { if (n == 0) { count_zero++; } else if (n == 1) { pairs += count_zero; } if (pairs > 1000000000) { return -1; } } return pairs; } 출처 : https://app.codility.com/programmers/lessons/5-prefix_sums/passing_cars/

...더보기 A small frog wants to get to the other side of a river. The frog is initially located on one bank of the river (position 0) and wants to get to the opposite bank (position X+1). Leaves fall from a tree onto the surface of the river. You are given an array A consisting of N integers representing the falling leaves. A[K] represents the position where one leaf falls at time K, measured in se..