[Lesson 2] Cycle Rotation

문제

An array A consisting of N integers is given. Rotation of the array means that each element is shifted right by one index, and the last element of the array is moved to the first place. For example, the rotation of array A = [3, 8, 9, 7, 6] is [6, 3, 8, 9, 7] (elements are shifted right by one index and 6 is moved to the first place).The goal is to rotate array A K times; that is, each element of A will be shifted to the right K times.Write a function:vector<int> solution(vector<int> &A, int K);that, given an array A consisting of N integers and an integer K, returns the array A rotated K times.For example, given A = [3, 8, 9, 7, 6] K = 3the function should return [9, 7, 6, 3, 8]. Three rotations were made: [3, 8, 9, 7, 6] -> [6, 3, 8, 9, 7] [6, 3, 8, 9, 7] -> [7, 6, 3, 8, 9] [7, 6, 3, 8, 9] -> [9, 7, 6, 3, 8]For another example, given A = [0, 0, 0] K = 1the function should return [0, 0, 0]Given A = [1, 2, 3, 4] K = 4the function should return [1, 2, 3, 4]Assume that:N and K are integers within the range [0..100];each element of array A is an integer within the range [−1,000..1,000].In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.

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풀이

리스트의 가장 마지막 원소를 변수에 담아두고, 원소들을 오른쪽으로 한칸씩 복사시켜 이동시킨다.

그 후 리스트의 0번째 자리의 값을 변수의 값으로 변경한다.

 

 

 

 

첫번째 제출  score : 87

// you can use includes, for example:
// #include <algorithm>

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

vector<int> solution(vector<int> &A, int K) {
    // Implement your solution here

    for(int i = 0; i < K ; i ++)
    {
        int lastnum = A.back();
        for(int j = A.size() - 1; j > 0; j--)
        {
            A[j] = A[j-1];
        }

        A[0] = lastnum;
    }

    return A;
}

빈 배열일 때를 고려하지 못했다.

 

두번째 제출 score : 100

 

빈 배열일 경우 탐색하지 않고 바로 리턴하도록 수정하였다.

if(A.empty()) return A;

// you can use includes, for example:
// #include <algorithm>

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

vector<int> solution(vector<int> &A, int K) {
    // Implement your solution here
    if(A.empty()) return A;
    
    for(int i = 0; i < K ; i ++)
    {
        int lastnum = A.back();
        for(int j = A.size() - 1; j > 0; j--)
        {
            A[j] = A[j-1];
        }

        A[0] = lastnum;
    }

    return A;
}

 

굳

 

 

REF

https://stackoverflow.com/questions/63799396/whats-the-difference-between-vectorint-a-and-vectorint-a