该项目是一个基本的ATM程序。我正在使用文件存储所有帐户详细信息。因此，每次运行.exe文件时，它都会从文件中读取数据并将其插入到AVL树中。当我关闭程序时，AVL节点中的所有数据都将插回到文件中。
数据按此顺序存储在文件中（每个数字用换行符分隔）ID，密码，名称，添加，城市，固定，平衡。 示例文件 -
12
4576
Vert
No_999,GoLane
Dallas
89777
50000
16
2342
Nerd
No_888,FoLane
Chicago
89999
30000
问题是我无法将数据写回文件。有什么建议吗？ 附：请原谅我的内联课程方法... 程序 -
#include<iostream>
#include<conio.h>
#include<string.h>
#include<fstream>
using namespace std;
fstream file("one2.txt",ios::in|ios::out);//Opening the file 'one2.txt' in global scope
//AVL tree code starts here
class avl
{
struct node //The structure node which is going to hold the data sets in the tree
{
int id,pwd;
char name[15],add[30],city[10];
int pn;
double bal;
node *left, *right;
int height;
//node constructors
node(int i,int p,char nam[15], char a[30], char c[10],int pin,double b, node * l,node * r,int h)
{
id=i;
pwd=p;
strcpy(name,nam);
strcpy(add,a);
strcpy(city,c);
pn=pin;
bal=b;
left=l;
right=r;
height=h;
}
node()
{
left=right=NULL;
id=pwd=pn=0;
bal=0;
height=-1;
}
};
node *root;
node *nullnode;
int Height(node *t)const //Func to return the height of a node
{
return((t==NULL)? -1:t->height);
}
int max(int a,int b)
{
return(a>b)?a:b;
}
//Beginning of Insert() -- To create and insert data into the nodes
void insert(const int &x,int p, char nam[15], char a[30], char c[10],int pin,double b, node *&t)
{
if(t==NULL)
t = new node(x,p,nam,a,c,pin,b,NULL,NULL,-1);
else if(x<t->id)
{
insert(x,p,nam,a,c,pin,b,t->left);
if(Height(t->left) - Height(t->right)==2)
{
if(x<t->left->id)
single_rotate_with_left(t);
else
double_rotate_with_left(t);
}
}
else if(x>t->id)
{
insert(x,p,nam,a,c,pin,b,t->right);
if(Height(t->right)-Height(t->left)==2)
{
if(x>t->right->id)
single_rotate_with_right(t);
else
double_rotate_with_right(t);
}
}
else
t->height=max(Height(t->left),Height(t->right)+1);
}
//End of insert()
//Func to print the node data. Just a sample to check if all the data
// were inserted into the tree
//Inorder traversal
void print(node *&t)
{
if(t!=NULL)
{
print(t->left);
cout<<endl;
cout<<"ID "<<t->id<<" Name "<<t->name;
cout<<endl<<t->pwd<<endl<<t->add<<"\n"<<t->city;
cout<<"-"<<t->pn<<endl<<t->bal<<endl;
print(t->right);
}
}
//Think there's gonna be no problem with the rotation and other AVL tree func codes.
//Beginning of AVL rotations
void single_rotate_with_left(node *&k2)
{
node *k1=k2->left;
k2->left=k1->right;
k1->right=k2;
k2->height=max(Height(k2->right),Height(k2->left))+1;
k1->height=max(Height(k1->left),(k2->height))+1;
k1=k2;
}
void single_rotate_with_right(node *&k2)
{
node *k1=k2->right;
k2->right=k1->left;
k1->left=k2;
k2->height=max(Height(k2->left),Height(k2->right))+1;
k1->height=max(Height(k1->right),(k2->height))+1;
k1=k2;
}
void double_rotate_with_left(node *&a)
{
single_rotate_with_right(a->left);
single_rotate_with_left(a);
}
void double_rotate_with_right(node *&a)
{
single_rotate_with_left(a->right);
single_rotate_with_right(a);
}
//End of AVL rotations
//Function to return the node. The 'id' variable to be searched is passed as a param
node*& search(int x,node *&t)
{
if(t->id>x)
return search(x,t->left);
else if(t->id<x)
return search(x,t->right);
else if(t->id==x)
{
return t;
}
else
return nullnode;
}
//End of search. I'm using this in the loadnode() function.
//This is where I try to write data back into the file.
void update1(node *&t,int x) // x is the control variable
{
if(x==1)
//This block will be executed only once when the function is called for the
//first time. Used to seek to the beginning of the file
{
file.seekg(0,ios::beg);
x++;
}
if(t!=NULL)// Inorder traversal in the tree
{
update1(t->left,x);
//writing the data in the same order as it was stored.
file<<t->id<<endl;
file<<t->pwd<<endl;
file<<t->name<<endl;
file<<t->add<<endl;
file<<t->city<<endl;
file<<t->pn<<endl;
file<<t->bal<<endl;
update1(t->right,x);
}
}
public:
//Avl Constructor - This one is the one which is actually used.
avl(int x,int p,char nam[15], char a[30], char c[10],int pin,double b)
{
root= new node(x,p,nam,a,c,pin,b,NULL,NULL,-1);
nullnode=new node;
}
avl()
{
root->left=root->right=NULL;
root->height=-1;
}
//Call to the private insert function
void insert1(const int &x,int p,char nam[15], char a[30], char c[10],int pin,double b)
{
insert(x,p,nam,a,c,pin,b,root);
}
//Call to the private print() function
void display()
{
cout<<endl;
print(root);
}
//Function to write a new value for 'bal' variable to a node.
//I'm actually using this to update a node anconfirm whether the value of the updated node
//is reflected back at the node
void loadnode(int x)
{
node *&t=search(x,root);
cout<<"\nLoaded node...\n";
cout<<t->id;
cout<<" "<<t->name;
t->bal=40000;
cout<<"\nUpdated Bal.."<<t->bal;
}
void update()
{
//file.seekp(0);
update1(root,1);
}
};//End of AVL Class
main()
{
cout<<"The output..\n";
int i, p, pn;
char n[15],a[30],c[10];
double b;
int prev_id=0;
file>>i>>p>>n>>a>>c>>pn>>b;
prev_id=i;
avl list(i,p,n,a,c,pn,b);
while(file)
{
file>>i>>p>>n>>a>>c>>pn>>b;
if(prev_id!=i)
// I'm using this because i got a weird scenario in which the last record was repeated twice.
{
list.insert1(i,p,n,a,c,pn,b);
}
prev_id=i;
}
cout<<endl<<"The elements in AVL tree are...\n\n";
list.display();
list.loadnode(12);//12 is the id i used for one of my records.
//Calling to write back the data into the file.
list.update();
file.close();
getch();
return 0;
}
//End of program
答案 0 :(得分：0)
调用seekp()将写指针移动到流的开头（fstream）。 seekg()移动get指针 - 写入时不会有帮助......
答案 1 :(得分：0)
如果file.good（）返回false，则对文件的某些先前操作失败（甚至可能是读取操作）并引发文件对象的错误标志之一。解决它的一种丑陋方法是使用file.clear（）来清除错误标志并允许下一步操作成功执行。解决问题的更好方法是在每次操作后检查是否存在错误（file.good（）为false）并理解为什么此操作失败并修复它。