题解 | 【模板】栈的操作

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

typedef struct Stack {
	int date;
	struct Stack* before;
	struct Stack* end;
}Stack;
void push(Stack* head, int x) {
	Stack* p = head->end;
	Stack* s = (Stack*)malloc(sizeof(Stack));
	s->date = x;
	s->before = p;
	s->end = NULL;
	head->end = s;
	head->date++;
}
void pop(Stack* head) {
	Stack* p = head->end;
	head->end = p->before;
	head->date--;
	free(p);
}
int query(Stack* head) {
	Stack* p = head->end;
	return p->date;
}
int size(Stack* head) {
	return head->date;
}
void analysis(char* command, Stack* head) {
	if (command[0] == 'p') {
		if (command[1] == 'u') {
			int i = 5;
			int sum = 0;
			int flag = 1;
			if (command[i] == '-') {
				i++;
				flag = -1;
			}
			while (command[i] != '\0') {
				sum = sum * 10 + command[i++] - 48;
			}
			push(head, flag * sum);
		}
		else if (command[1] == 'o') {
			if (size(head) > 0) {
				pop(head);
			}
			else {
				printf("Empty\n");
			}
		}
	}
	else if (command[0] == 'q') {
		if (size(head) > 0) {
			printf("%d\n", query(head));
		}
		else {
			printf("Empty\n");
		}
	}
	else if (command[0] == 's') {
		printf("%d\n", size(head));
	}
	else {
		printf("输入错误");
	}
}
int main() {
	Stack head;
	head.date = 0;
	head.before = NULL;
	head.end = &head;
	int T = 0;
	scanf("%d", &T);
	char command[20];
	while (T--) {
		getchar();
		scanf("%[^\n]", command);
		analysis(command, &head);
	}
	return 0;
}