poj1028 類比瀏覽器後退和前進（棧）

        題目是讓類比實現一下瀏覽器的後退和前進功能，題目中也有提示，用兩個棧就可以了，比較簡單。

#include <stdio.h>#include <stdlib.h>#include <string.h>typedef struct {int top;//棧頂char* s[100];} Stack;/***初始化*/Stack* create_stack(){Stack* stack=(Stack*)(malloc(sizeof(Stack)));stack->top=-1;memset(stack->s,0,sizeof(stack->s));return stack;}void push(Stack* stack,char* str){stack->s[++stack->top]=str;}char* pop(Stack* stack){int top=stack->top;if(top==-1){return NULL;}stack->top--;return stack->s[top];}int isEmpty(Stack* stack){return stack->top==-1;}int main(void){Stack* forward=create_stack();Stack* backward=create_stack();char* home_page="http://www.acm.org/";char* current_page=home_page;char command[8];while(1){scanf("%s",command);if(command[0]=='Q'){//QUITbreak;}else if(command[0]=='V'){//VISITpush(backward,current_page);char *str=(char*)malloc(sizeof(char)*71);scanf("%s",str);current_page=str;forward->top=-1;printf("%s\n",str);}else if(command[0]=='B'){//BACKif(isEmpty(backward)){printf("Ignored\n");}else{push(forward,current_page);current_page=pop(backward);printf("%s\n",current_page);}}else{//FORWARDif(isEmpty(forward)){printf("Ignored\n");}else{push(backward,current_page);current_page=pop(forward);printf("%s\n",current_page);}}}int i;for(i=0;i<100;i++){//釋放下堆記憶體.....char* tmp=backward->s[i];if(tmp&&tmp!=home_page){free(backward->s[i]);}}free(forward);free(backward);return 0;}