数据结构之栈的应用车厢调度的问题

题目：借助栈 把字符数组train中的字符S都调到字符H的前面
示例：“HSHSHSHSHS”-->"SSSSSHHHHH"
出错描述：编译器显示 弹出“停止工作”窗口

 # include<stdio.h>
# define n 20
# define OK 1
# define ERROR 0
# define TRUE 1
# define FALSE 0
typedef int status;
typedef char ElemType;
typedef struct
{
    ElemType data[n];
    int top;
}SqStack;
void Init_Sq(SqStack *S)
{
    S->top=-1; 
}
status Push_Sq(SqStack *S,ElemType e)
{
    if(S->top+1==n)
        return ERROR;
    S->data[++S->top]=e;
    return OK;  
}
status Pop_Sq(SqStack *S,ElemType *e)
{
    if(S->top==-1) 
        return ERROR;
    *e=S->data[S->top--];
    return OK;  
}
status EmptyStack_Sq(SqStack S)
{
    if(S.top==-1)
        return TRUE;
    else
        return FALSE;
}
status Train_Arrange(char *train)
{ 
    char *p=train,*q=train,e;
    SqStack S;
    Init_Sq(&S);  
    while(*p)
    {//HSHSHSHSHS  
        if(*p=='H')
        {
            Push_Sq(&S,*p);
            printf("p==%p\n",*p);
        }
        else
            *(q++)=*p;
        p++; 
    }
    while(EmptyStack_Sq(S)==FALSE) 
    {
        Pop_Sq(&S,&e);
        *(q++)=e;//这儿也有问题，但是不清楚原因 
    }
    return OK;
} 
void Traverse_Sq(char *train)
{
    ElemType *p;
    p=train;
    while(*p!='\0')
        printf("%c",*p++);
    printf("\n");
}
int main()
{
    char *train="HSHSHSHSHS";
    Train_Arrange(train);
    printf("转换后的火车序列为:");
    Traverse_Sq(train);
    return 0;
}

int main()
{
char train[100]="HSHSHSHSHS";
Train_Arrange(train);
printf("转换后的火车序列为:");
Traverse_Sq(train);
return 0;
}
main 函数中把char * train修改为char train[100];使用char * train=""时，指针指向字符串被当作常量而且被放置在此程序的内存静态区，不允许修改，改为数组就ok了。