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Queue2.java
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Queue2.java
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package Baekjoon.DataStructure;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
//24-10-14 20min
// https://www.acmicpc.net/problem/18258
public class Queue2 {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
StringTokenizer st;
int cmdNum = Integer.parseInt(br.readLine());
int[] queue = new int[cmdNum];
int lastIdx = -1; // 마지막으로 들어 있는 idx
int firstIdx = 0; // 빠져나갈 idx
while (cmdNum-- > 0) {
st = new StringTokenizer(br.readLine());
String cmd = st.nextToken();
switch (cmd) {
case "push":
int num = Integer.parseInt(st.nextToken());
queue[++lastIdx] = num;
break;
case "pop":
if (lastIdx < firstIdx) {
sb.append(-1).append("\n");
} else {
sb.append(queue[firstIdx++]).append("\n");
}
break;
case "size":
sb.append(lastIdx - firstIdx + 1).append("\n");
break;
case "empty":
if (lastIdx < firstIdx) {
sb.append(1).append("\n");
} else {
sb.append(0).append("\n");
}
break;
case "front":
if (lastIdx < firstIdx) {
sb.append(-1).append("\n");
} else {
sb.append(queue[firstIdx]).append("\n");
}
break;
case "back":
if (lastIdx < firstIdx) {
sb.append(-1).append("\n");
} else {
sb.append(queue[lastIdx]).append("\n");
}
break;
default:
}
}
System.out.println(sb);
}
}