java - c++ 数据结构这个错在哪了，动态存储？

问题描述

找了半天了，麻烦帮我看下。

///////////头文件#ifndef POSTMASTER_H_INCLUDED#define POSTMASTER_H_INCLUDED#include<iostream>#include <stdio.h>#include <tchar.h>using namespace std;class Matrix{ int rows, columns; int **element; void init(int rows, int columns);public:Matrix(int rows, int columns,int x); ~Matrix(); friend ostream& operator<<(ostream& out, Matrix&); };#endif // POSTMASTER_H_INCLUDED////////////////////.cpp#include 'wine.h'void Matrix::init(int rows, int columns){ element = new int*[rows]; this->rows = rows; this->columns = columns; for (int i = 0;i < columns;i++) {element[i] = new int[columns]; }}Matrix::Matrix(int rows, int columns, int x){ this->init(rows, columns); cout << '1'; for (int i = 0;i < rows;i++)for (int j = 0;j < columns;j++) { element[i][j]=x; ///这里貌似出错了？}}Matrix::~Matrix(){ for (int i = 0;i < rows;i++) {delete element[i]; //delete[] element[i]; ? } delete element;}ostream& operator<<(ostream& os, Matrix&a){ os<< '矩阵(' << a.rows << ',' << a.columns << '):' << endl; for (int i = 0;i < a.rows;i++) {os<< endl;for (int j = 0;j < a.columns;j++) os << a.element[i][j]<<' '; } return os;}//////////////////main()#include 'wine.h'#include 'wine.cpp'#include<iostream>#include<cstdlib>using namespace std;int main(){ int b[3][2] = { 1,2,3,4,5,6 }; Matrix a(3,2,4); cout << a; system('PAUSE'); return 0;}

问题解答

错误的关键在这一行：

element[i][j] = x;

这种寻址的使用方式会尝试访问element(首地址)+i*sizeof(int*)+j*sizeof(int)。最好还是乖乖地使用：

int* row = element[i];row[j] = x;

比较稳妥一些，也不怕不同的编译器有不同的解释方法。

for (int i = 0;i < columns;i++)改为for (int i = 0;i < rows;i++)