코딩테스트 입문 - Day 24

치킨 쿠폰

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class Solution {
    public int solution(int chicken) {
        int answer = 0;
        int remain = 0;
        while(chicken > 0){
            remain += chicken % 10;
            answer += chicken /= 10;
        }
        int remain2 = 0;
        while(remain > 0){
            remain2 += remain % 10;
            answer += remain /= 10;
        }
        
        return answer + remain2 /10;
    }
}

이진수 더하기

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class Solution {
    public String solution(String bin1, String bin2) {
        int num1 = switchNum(bin1);
        int num2 = switchNum(bin2);
        int sum = num1 + num2;

        StringBuilder sb = new StringBuilder();
        while (sum > 0) {
            sb.append(sum % 2);
            sum /= 2;
        }
        
        if(sb.toString().isEmpty()){
            return "0";
        }
        return sb.reverse().toString();
    }

    public static int switchNum(String s) {
        int num = 0;
        int n = 1;
        for (int i = s.length() - 1; i >= 0; i--) {
            if (s.charAt(i) == '1') {
                num += n;
            }
            n *= 2;
        }
        return num;
    }
}

A로 B만들기

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import java.util.*;

class Solution {
    public int solution(String before, String after) {
        StringBuilder sb = new StringBuilder();
        HashMap<String, Integer> hm = new HashMap<>();
        for(int i = 0 ; i< before.length();i++){
            String s = before.substring(i,i+1);
            if(!hm.containsKey(s)){
                hm.put(s,1);
                continue;
            }
            hm.put(s, hm.get(s) + 1);
        }
        
        for(int i = 0; i< after.length(); i++){
            String s = after.substring(i,i+1);
            if(!hm.containsKey(s)){
                return 0;
            }
            hm.put(s, hm.get(s) - 1);
        }
        
        for(String s : hm.keySet()){
            if(hm.get(s) != 0){
                return 0;
            }
        }
        return 1;
    }
}

k의 개수

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class Solution {
    public int solution(int i, int j, int k) {
        String strk = k +"";
        int answer = 0;
        for(int l = i; l <= j; l++){
            int leng = (l+"").length();
            int len = (l+"").replace(strk,"").length();
            if(leng != len){
                answer += (leng - len) ;
            }
        }
        return answer;
    }
}