Question

我用c++运行代码的时候出现了图片里面的错误，麻烦大家看一下该怎么改过来~~~

#include<stdio.h>#include<malloc.h>
#include<string.h>
#define M 20
#define elemtype char
typedef struct
{
elemtype stack[M];
int top;
}
stacknode;
void init(stacknode *st);
void push(stacknode *st,elemtype x);
void pop(stacknode *st);
void init(stacknode *st){
st->top=0;
}
void push(stacknode *st,elemtype x){
if(st->top==M)
printf("the stack is overflow!\n");
else
{
st->top=st->top+1;
st->stack[st->top]=x;
}
}
void pop(stacknode *st){
if(st->top>0) st->top--;
else printf("Stack is Empty!\n");
}
int main(){
char s[M];
int i;
stacknode *sp;
printf("create a empty stack!\n");
sp=malloc(sizeof(stacknode));
init(sp);
printf("input a expression:\n");
gets(s);
for(i=0;i<strlen(s);i++)
{
if(s[i]=='(')
push(sp,s[i]);
if(s[i]==')')
pop(sp);
}
if(sp->top==0)
printf("'('match')'!\n");
else
printf("'('not match')'!\n");
return 0;
}

Answer 1

sp=malloc(sizeof(stacknode));这里需要强制类型转换为stacknode*
sp=(stacknode*)malloc(sizeof(stacknode));
第二个错误无所谓的，没有特别危害