10845번: 큐

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

int q[10000];

int start = 0, end = 0, count = 0;

void push(int x);

void pop();

void size();

void empty();

void front();

void back();

void push(int x)

{

q[end++] = x;

++count;

}

void pop()

{

if (count != 0)

{

printf("%d\n", q[start++]);

--count;

}

else

printf("-1\n");

}

void size()

{

printf("%d\n", count);

}

void empty()

{

if (count == 0)

printf("1\n");

else

printf("0\n");

}

void front()

{

if (count != 0)

printf("%d\n", q[start]);

else

printf("-1\n");

}

void back()

{

if (count != 0)

printf("%d\n", q[end-1]);

else

printf("-1\n");

}

int main()

{

int N;

scanf("%d", &N);

for (int i = 0; i < N; ++i)

{

char command[6];

int x;

scanf("%s", &command);

if (!strcmp(command, "push"))

{

scanf("%d", &x);

push(x);

}

else if (!strcmp(command, "pop"))

pop();

else if (strcmp(command, "size") == 0)

size();

else if (strcmp(command, "empty") == 0)

empty();

else if (strcmp(command, "front") == 0)

front();

else if (strcmp(command, "back") == 0)

back();

}

}