Header.h

Question

我在cpp。

的头文件中使用extern变量时遇到了一些问题

所以我的（简化的）cppfiles如下：

Header.h

#ifndef HEADER_H
#define HEADER_H
#include <string>
#include <list>

struct BstNode;
class Point;
extern std::list<Point> coordinates;
BstNode* Insert(BstNode* root, int data, std::string position);
void IterateLeft(BstNode* root);
void IterateRight(BstNode* root);
bool SearchAll(BstNode* root,int data);
int CalculateHeight(BstNode* root);
int CalculateWidth(BstNode* root);

#endif

MainFile.cpp

#include <iostream>
#include "Header.h"
using namespace std;

BstNode* TestFunction();

int main() {
    BstNode* testTree = TestFunction();
    cout<<"\nWidth: "<<CalculateWidth(testTree)<<"\n";
    cout<<"\nHeight: "<<CalculateHeight(testTree)<<"\n";
    system("pause");

    return 0;
}

BstNode* TestFunction() {
    cout<<"Creating test-structure...";
    BstNode* testTree = NULL;
    testTree = Insert(testTree,17,""); //cout<<"17";
    testTree = Insert(testTree,16,"0"); //cout<<"16";
    testTree = Insert(testTree,15,"00"); //cout<<"15";
    testTree = Insert(testTree,14,"000"); //cout<<"14";
    testTree = Insert(testTree,13,"0000"); //cout<<"13";
    testTree = Insert(testTree,12,"00000"); //cout<<"12";
    testTree = Insert(testTree,8, "001"); //cout<<"8";
    testTree = Insert(testTree,7, "0010"); //cout<<"7";
    testTree = Insert(testTree,21,"0011"); //cout<<"21";
    testTree = Insert(testTree,20,"00110"); //cout<<"20";
    return testTree;
}

Casual.cpp

#include<iostream>
#include<string>
#include<algorithm>
#include<list>
#include<math.h>
#include "Header.h"
using namespace std;

//Node Definition
struct BstNode {
    int data; 
    BstNode* left;
    BstNode* right;
};

BstNode* GetNewNode(int data) {
    BstNode* newNode = new BstNode();
    newNode->data = data;
    newNode->left = newNode->right = NULL;
    return newNode;
}

BstNode* testTree = NULL;

// Class to represent points.
class Point {
private:
    int xval, yval, val;
public:
    Point(int x=0, int y=0, int v=0) {
        xval = x;
        yval = y;
        val = v;

    }

    int x() { return xval; }
    int y() { return yval; }
    int v() { return val; }

    friend bool operator== (const Point a,const Point b) {
        return (a.xval==b.xval && a.yval==b.yval);
    }
};


// Calculates width
int CalculateWidth(BstNode* root){
    int width;
    if (root->left==NULL && root->right==NULL) {/*cout<<"leaf\n";*/ width = 1;}
    else {
        if (root->left==NULL) {width = CalculateWidth(root->right); /*cout<<"left=NULL\n";*/}
        if (root->right==NULL) {width = 1 + CalculateWidth(root->left); /*cout<<"right=NULL\n";*/}
    }
if (root->left!=NULL && root->right!=NULL) width = max(1+CalculateWidth(root->left),CalculateWidth(root->right));   
    return width;
}

// Calculates height of svg
int x=0,y=0;
list<Point> coordinates;
void IterateLeft(BstNode* root);
void IterateRight(BstNode* root);
int CalculateHeight(BstNode* root) {
    int height=0;
    int highest=0;
    int lowest=0;
    cout<<"check";                              // /////////THIS WILL BE DISPLAYED
    coordinates.push_front(Point(x,y,root->data));
    cout<<"check";                              // /////////THIS WONT ANYMORE
    if(root->left!=NULL) IterateLeft(root->left);
    if(root->right!=NULL) IterateRight(root->right);
    for (list<Point>::iterator i = coordinates.begin(); i!=coordinates.end(); i++) {
        if((*i).y()>highest) highest = (*i).y();
        if((*i).y()<lowest ) lowest  = (*i).y();
    cout<<"("<< (*i).x() << "," << (*i).y() << ")\n";}

    height = highest - lowest + 1;
    return height;  
}

// Helpfunction for CalculateHeight
void IterateLeft(BstNode* root) {
    x++;
    if(find(coordinates.begin(),coordinates.end(),Point(x,y))!=coordinates.end()) {IterateRight(root);}
    else {
        coordinates.push_front(Point(x,y,root->data));
        if(root->left!=NULL) IterateLeft(root->left);
        if(root->right!=NULL) IterateRight(root->right);
    }
    x--;
} 
// Helpfunction for CalculateHeight
void IterateRight(BstNode* root) {
    if(y>0) {y=y*(-1);}
    else {y=y*(-1)+1;}
    bool occupied = false;
    for(int bench = CalculateWidth(root); bench>=0; bench--) {
        if(find(coordinates.begin(),coordinates.end(),Point(x+bench,y))!=coordinates.end()) occupied=true;
    }
    if(occupied) {IterateRight(root);}
    else {
        coordinates.push_front(Point(x-1,y,root->data));
        coordinates.push_front(Point(x,y,root->data));
        if(root->left!=NULL) IterateLeft(root->left);
        if(root->right!=NULL) IterateRight(root->right);
    }
    if(y>0) {y=(y-1)*(-1);}
    else {y=y*(-1);}

}

// Insert a new node at a certain Position: 0 means left - 1 means right
BstNode* Insert(BstNode* root, int data, string position){
    if (root == NULL) {
        if (position.empty()) {
            root = GetNewNode(data);
        }
        else {
            root = GetNewNode(0);
            Insert(root,data,position);
        }
    }
    else {
        if (position.empty()) {
            root = GetNewNode(data);
        }
        else {
            if (position[0] == '0') {
                root->left = Insert(root->left,data,position.erase(0,1));
            }
            else {
                root->right = Insert(root->right,data,position.erase(0,1));
            }
        }
    }
    return root;
}


//Looks for an element in Tree everywhere -> true if found
bool SearchAll(BstNode* root,int data) {
    if(root == NULL) {
        return false;
    }
    else if(root->data == data) {
        return true;
    }
    else {
        return (SearchAll(root->left,data) | SearchAll(root->right,data));
    }
}

现在当我编译它时，它将编译。但是在运行该程序时，它会中止告诉我

CXX0030：错误：无法评估表达式

任何人都有任何暗示问题可能是什么？

错误出现在CalculateHeight定义中的Casual.cpp中。该行说：

coordinates.push_front(Point(x,y,root->data));

Answer 1

添加

的定义后

BstNode* GetNewNode( int d ){
  BstNode* res = new BstNode();
  res->data = d;
  return res;
}

程序执行：

Creating test-structure...
Width: 6
checkcheck(3,-1)
(2,-1)
(1,-1)
(3,1)
(2,1)
(1,1)
(5,0)
(4,0)
(3,0)
(2,0)
(1,0)
(0,0)

Height: 3

我没有验证这个; - ）

在Cpp-header中使用extern变量

Header.h

MainFile.cpp

Casual.cpp

1 个答案: