단체사진찍기

dfs로 접근

순열을 dfs로 하여 문제를 푼다

import java.util.HashMap;

public class GroupPhoto {
    static String[] d;
    static HashMap<Character, Integer> map;
    static boolean[] visited;
    static int[] ch;
    static int answer;

    public static void main(String[] args) {
        int n = 2;
        String[] data = {
                "N~F=0",
                "R~T>2"
        };

        d=data;
        map = new HashMap<>();
        visited = new boolean[8];
        ch = new int[8];
        answer =0;
        map.put('A',0);
        map.put('C',1);
        map.put('F',2);
        map.put('J',3);
        map.put('M',4);
        map.put('N',5);
        map.put('R',6);
        map.put('T',7);
        dfs(0);
    }

    static void dfs(int idx){
        if(idx == 8){
            if(check()) answer++;
        }
        else{
            for(int i=0; i<8; i++){
                if(!visited[i]){
                    visited[i] = true;
                    ch[idx] = i;
                    dfs(idx + 1);
                    visited[i] = false;
                }
            }
        }
    }

    static boolean check(){
        int a,b,res;
        char op;
        for(String s : d){
            a = ch[map.get(s.charAt(0))];
            b = ch[map.get(s.charAt(2))];
            op = s.charAt(3);
            res = s.charAt(4)-'0'+1;

            if(op == '='){
                if(Math.abs(a-b)!=res) return false;
            }
            else if(op == '>'){
                if(Math.abs(a-b) <= res) return false;
            }
            else{
                if(Math.abs(a-b) >= res) return false;
            }
        }
            return true;
    }
}