백준) 2812_크게 만들기

https://www.acmicpc.net/problem/2812

2812번: 크게 만들기

 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
import java.util.StringTokenizer;
 
public class number_2812 {
 
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int N = Integer.parseInt(st.nextToken());
        int K = Integer.parseInt(st.nextToken());
        String number = br.readLine();
 
        StringBuilder sb = new StringBuilder();
 
        Stack<Integer> stack = new Stack<>();
 
        for (int i = 0; i < number.length(); i++) {
            int num = number.charAt(i) - '0';
            if (stack.isEmpty()) {
                stack.push(num);
                continue;
            } 
 
            while (!stack.isEmpty() && stack.peek() < num) {
                if (stack.size() + number.length() - (i + 1) < N - K) {
                    break;
                }
                stack.pop();
            } 
            stack.push(num);
            
        }
        
        while (stack.size() != N - K) {
            stack.pop();
        }
        
        for (int value : stack) {
            sb.append(value);
        }
        System.out.println(sb.toString());
    }
}