洗掉陣列指標時我的程式不回傳0

當我嘗試洗掉宣告為的陣列指標時

short *width = NULL;
width = new short[lenght];
delete[] width;

程式在洗掉部分停止并回傳一個亂數。

這是我的所有程式

int main(){
    short **junction = NULL, *width = NULL, length = 0;
    ifstream input;

    input.open("sample_input.txt");
    if(!input)
        cout << "No such a file named \"sample_input.txt\"" << endl;
    else if(input >> length){
        junction = new short*[length];
        width = new short[length];
        string str; 
        for(int i = 0; i - 1 < length && getline(input, str); i  ){
            istringstream ss(str);
            width[i - 1] = (str.size()   1) / 2; //numbers can be two char, so in this case, here we allocate more than necessary memory
            junction[i - 1] = new short[width[i - 1]];
            for(int j = 0; j < width[i - 1]; j  ){
                if(ss.eof()){
                    junction[i - 1][j] = -1; // -1 is the key value of emtpy spaces
                    continue;
                }
                ss >> junction[i - 1][j];
            }
        }
    }
    input.close();

    /*
    for(int i = 0; i < length; i  )
        delete[] junction[i];
    delete[] junction;
    delete[] width;
    */

    return 0;
}

評論部分有問題，我單獨嘗試了那些洗掉陳述句，只是因為部分正在運行，但不像我預期的那樣，這是我的示例輸入：

uj5u.com熱心網友回復：

您的代碼實際上應該沒問題。請向我們展示整個程式。

florian@florian-desktop:~$ cat -n test2.cpp
     1  #include <iostream>
     2  int main()
     3  {
     4  const int length = 4;
     5  short *width = NULL;
     6  width = new short[length];
     7  delete[] width;
     8  }
florian@florian-desktop:~$ valgrind ./a.out 
==22630== Memcheck, a memory error detector
==22630== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==22630== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==22630== Command: ./a.out
==22630== 
==22630== 
==22630== HEAP SUMMARY:
==22630==     in use at exit: 0 bytes in 0 blocks
==22630==   total heap usage: 2 allocs, 2 frees, 72,712 bytes allocated
==22630== 
==22630== All heap blocks were freed -- no leaks are possible
==22630== 
==22630== For lists of detected and suppressed errors, rerun with: -s
==22630== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Valgrind 顯示所有保留的記憶體都已正確釋放。

- 更新：

我更正了您的完整代碼：

#include <iostream>
#include <sstream>
#include <fstream>
using namespace std;
int main() {
short **junction = NULL, *width = NULL, length = 12;
    ifstream input;

    input.open("sample_input.txt");
    if(!input)
        cout << "No such a file named \"sample_input.txt\"" << endl;
    else if(input >> length){
        junction = new short*[length];
        width = new short[length];
        string str; 
        for(int i = 0; i < length && getline(input, str); i  ){
            istringstream ss(str);
            width[i] = (str.size()   1) / 2; //numbers can be two char, so in this case, here we allocate more than necessary memory
            junction[i] = new short[width[i]];
            for(int j = 0; j < width[i]; j  ){
                if(ss.eof()){
                    junction[i][j] = -1; // -1 is the key value of emtpy spaces
                    continue;
                }
                ss >> junction[i][j];
            }
        }
    }
    input.close();

    
    for(int i = 0; i < length; i  )
        delete[] junction[i];
    delete[] junction;
    delete[] width;
    

    return 0;
}

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