Day 10 - 코딩테스트 입문(Java)

1. 점의 위치 구하기

https://school.programmers.co.kr/learn/courses/30/lessons/120841

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int[] dot) {
        int answer = 0;
        int x = dot[0];
        int y = dot[1];
        
        if(x > 0 && y > 0) {
            answer = 1;
        } else if(x < 0 && y > 0) {
            answer = 2;
        } else if(x < 0 && y < 0) {
            answer = 3;
        } else {
            answer = 4;
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(int[] dot) {
        int answer = 0;
        int x = dot[0];
        int y = dot[1];
        
        if(x > 0) {
            answer = y > 0 ? 1 : 4;
        } else if(x < 0) {
            answer = y > 0 ? 2 : 3;
        }
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public int solution(int[] dot) {
        int answer = 0;
        int x = dot[0];
        int y = dot[1];
        
        answer = x > 0 && y > 0 ? 1 : x < 0 && y > 0 ? 2 : x < 0 && y < 0 ? 3 : 4;
        
        return answer;
    }
}

 

2. 2차원으로 만들기

https://school.programmers.co.kr/learn/courses/30/lessons/120842

프로그래머스

▼ 방법 1

class Solution {
    public int[][] solution(int[] num_list, int n) {
        int[][] answer = new int[num_list.length / n][n];
        int idx = 0;
        
        for(int i = 0; i < answer.length; i++) {
            for(int j = 0; j < n; j++) {
                answer[i][j] = num_list[idx++];
            }
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int[][] solution(int[] num_list, int n) {
        int[][] answer = new int[num_list.length / n][n];
        
        for(int i = 0; i < answer.length; i++) {
            for(int j = 0; j < n; j++) {
                answer[i][j] = num_list[i * n + j];
            }
        }
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public int[][] solution(int[] num_list, int n) {
        int[][] answer = new int[num_list.length / n][n];
        
        for(int i = 0; i < num_list.length; i++) {
            answer[i / n][i % n] = num_list[i];
        }
        
        return answer;
    }
}

 

3. 공 던지기

https://school.programmers.co.kr/learn/courses/30/lessons/120843

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int[] numbers, int k) {
        int answer = 0;
        int idx = 0;
        
        for(int i = 0; i < k - 1; i++) {
            idx += 2;
            
            if(idx > numbers.length - 1) {
                idx -= numbers.length;
            }
            
            answer = numbers[idx];
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(int[] numbers, int k) {
        int answer = 0;
        
        answer = numbers[2 * (k - 1) % numbers.length];
        
        return answer;
    }
}

 

4. 배열 회전시키기

https://school.programmers.co.kr/learn/courses/30/lessons/120844

프로그래머스

▼ 방법 1

class Solution {
    public int[] solution(int[] numbers, String direction) {
        int[] answer = new int[numbers.length];
        
        if(direction.equals("left")) {
            for(int i = 1; i < numbers.length; i++) {
                answer[i - 1] = numbers[i];
            }
            
            answer[numbers.length - 1] = numbers[0];
        } else {
            answer[0] = numbers[numbers.length - 1];
            
            for(int i = 0; i < numbers.length - 1; i++) {
                answer[i + 1] = numbers[i];
            }
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int[] solution(int[] numbers, String direction) {
        int[] answer = new int[numbers.length];
        
        for(int i = 0; i < numbers.length; i++) {
            if(direction.equals("left")) {
                answer[i] = numbers[i == numbers.length - 1 ? 0 : i + 1];
            } else {
                answer[i] = numbers[i == 0 ? numbers.length - 1 : i - 1];
            }
        }
        
        return answer;
    }
}