개발공부

https://programmers.co.kr/learn/courses/30/lessons/42746

정렬 알고리즘 문제

import java.util.*;
class Solution {
    public String solution(int[] numbers) {
        String answer = "";
        String[] arr = new String[numbers.length];
        for(int i=0;i<numbers.length;i++){
            arr[i] = Integer.toString(numbers[i]);
        }
        Arrays.sort(arr, new Comparator<String>(){
           @Override
            public int compare(String str1, String str2){
                return (str2+str1).compareTo(str1+str2);
            }
        });
        
        if(arr[0].startsWith("0")){
            answer += "0";
        }else{
            for(String a : arr){
                answer += a;
            }
        }
        return answer;
    }
}

출처 : https://programmers.co.kr/learn/courses/30/lessons/12943?language=cpp 

#include <string>
#include <vector>

using namespace std;

int solution(int num) {
    int answer = 0;
    long long num1 = num;
    while (num1 != 1) {
        if (answer > 500) {
            return -1;
        }
        if (num1 % 2 == 0) {
            num1 = num1 / 2;
        } else {
            num1 = num1 * 3;
            num1++;
        }
        answer++;
    }
    return answer;
}

https://programmers.co.kr/learn/courses/30/lessons/42747

정렬 알고리즘

import java.util.*;

class Solution {
    public int solution(int[] citations) {
        int answer = 0;
        Arrays.sort(citations);
        for(int i=0;i<citations[citations.length-1];i++){
            answer = i;
            int cnt = 0;
            for(int j=0;j<citations.length;j++){
                if(answer < citations[j])
                    cnt++;
            }
            if(answer >= cnt)
                break;
            
        }
        return answer;
    }
}

출처 : https://www.acmicpc.net/problem/2941

string에 replace와 find함수를 사용했다.

#include <string>
#include <vector>
#include <iostream>
using namespace std;

int main(void) {
    vector<string> vString;
	string s;
	int n;
	vString.push_back("c=");
	vString.push_back("c-");
	vString.push_back("dz=");
	vString.push_back("d-");
	vString.push_back("lj");
	vString.push_back("nj");
	vString.push_back("s=");
	vString.push_back("z=");

	cin >> s;
	for (int i = 0; i < vString.size(); i++) {
		while (1) {
			n = s.find(vString[i]);
			if (n == string::npos) {
				break;
			}
			s.replace(n, vString[i].length(), "#");
		}
	}
	cout << s.length();
    
    return 0;
}

https://programmers.co.kr/learn/courses/30/lessons/42883

탐욕법 알고리즘 사용

class Solution {
    public String solution(String number, int k) {
        StringBuilder answer = new StringBuilder(number);
        int delCnt = 0;
        int index = 1;
        while(delCnt != k){
            if(index>=1 && answer.charAt(index-1) < answer.charAt(index)){
                answer.deleteCharAt(index-1);
                index--;
                delCnt++;
            }else{
                if(index == answer.length() - 1 && answer.charAt(index-1) >= answer.charAt(index)){
                    answer.deleteCharAt(index);
                    delCnt++;
                    index--;
                }else
                    index++;
            }
        }
        return answer.toString();
    }
}