빙글빙글

https://school.programmers.co.kr/learn/courses/30/lessons/64061

import java.util.ArrayList;
import java.util.Stack;
class Solution {
    public int solution(int[][] board, int[] moves) {
        int answer=0;
		ArrayList<Stack<Integer>> aa = new ArrayList<Stack<Integer>>();
		for(int i=0;i<board.length;i++)
			aa.add(new Stack<Integer>());
		for(int i=board.length-1;i>=0;i--) {
			for(int j=0;j<board.length;j++) {
				Stack<Integer> a = aa.get(j);
				if(board[i][j]==0)continue;
				else a.add(board[i][j]);
			}
		}
		Stack<Integer> bb = new Stack<Integer>();
		for(int i=0;i<moves.length;i++) {
			int b = moves[i]-1;
			Stack<Integer> cc = aa.get(b);
			if(cc.isEmpty())continue;
			int c = cc.pop();
			if(!bb.isEmpty()&&bb.peek()==c) {
				//.out.println("peek:"+bb.peek()+"pop:"+c);
				answer+=2;bb.pop();
			}
			else {
				bb.add(c);//System.out.println("peek:"+bb.peek());
			}
		}
		return answer;
    }
}

https://school.programmers.co.kr/learn/courses/30/lessons/131115

가격 순으로 정렬 후 하나만 보이게 하였다.

SELECT * from food_product order by price desc limit 1;

https://school.programmers.co.kr/learn/courses/30/lessons/142086

- Java

HashMap Key로 글자를 넣고

인덱스를 확인하며 갱신해주었다.

import java.util.*;
class Solution {
    public int[] solution(String s) {
        HashMap<Character,Integer> aa = new HashMap<>();
        int[] answer = new int[s.length()];
        for(int i=0;i<s.length();i++){
            char k = s.charAt(i);
            if(aa.containsKey(k)){
                answer[i]=i-aa.get(k);
                aa.put(k,i);
            }
            else{
                answer[i]=-1;
                aa.put(k,i);
            }
        }
        return answer;
    }
}

- Ruby

def solution(s)
    answer = []
    al = Array.new(26,-1)
    for i in 0..(s.length-1)
        a = s[i].ord-'a'.ord
        if al[a]==-1
            answer.append(-1)
        else
            answer.append(i-al[a])
        end
        
        al[a]=i
    end
    return answer
end