我写的char *函数似乎并不存储我从const char *字符串复制的值

Question

以下是昨天修改后的代码。它崩溃了我的void函数中删除tempChar的行。 我尝试使用delete [] tempChar;在我的char *函数中将tempStr作为全局变量;在删除tempChar之前先删除tempChar中的内容。两者都没有。

#include <iostream>
using namespace std;
#include <cstring>

char* string_reverse2(const char* string){
    cout << "the word to reverse: " << string << endl << endl;
    if (string == NULL){
        return NULL;
    }

    int strlength = strlen(string);
    char* tempStr = new char[strlength + 1];
    tempStr[strlength + 1] = 0;

    int index = 0;
    for (int i = 0; i <= strlength; i++){
        tempStr[index] = string[strlength - 1 - i];
        index++;
    }
    cout << endl;
    return tempStr;

}

void string_reverse1(char* string){
    char* tempChar = string_reverse2(string);
    cout << tempChar << endl;
    //delete tempChar;
}

int main(){
    string_reverse1("I love Friday!");
    return 0;
}

=============================================== =================================== 我从我的void string_reverse1函数中获取一个const char * string作为我的参数，并尝试通过将值复制到新创建的char * tempStr来反转它。在for循环中，我能够看到const char *字符串的每个值被成功复制到tempStr;但是，tempStr似乎在for循环之外是空的。你能帮我弄清楚问题是什么吗？ 非常感谢！

char* string_reverse2(const char* string) {
    cout << "the word to reverse: " << string << endl << endl;
    if (string == NULL){
        return NULL;
    }

    int strlength = strlen(string);
    char* tempStr = new char[strlength];

    for (int i = strlen(string); i >= 0; i--){
        tempStr[strlen(string) - i] = string[i];
        cout << tempStr[strlen(string) - i];        
    }

    cout << endl << endl;
    //tempStr[strlen(string) + 1] = '\0';
    cout << "reversed word: " << tempStr << endl;
    return tempStr;

}

void string_reverse1(char* string){
    const char* temp = string;
    char* tempChar = string_reverse2(temp);
    cout << tempChar;
}

Answer 1

我认为您可以按照这些建议（see live sample）

修复您的代码

#include <iostream>
#include <cstring>

using namespace std;

char* string_reverse2(const char* string) {
    cout << "the word to reverse: " << string << endl << endl;
    if (string == NULL){
        return NULL;
    }

    int strlength = strlen(string);
    char* tempStr = new char[strlength + 1];
                                    // ^^^
    // Ensure the NUL character at end of c-string
    tempStr[strlength + 1] = 0;

    int index = 0; // The inital index to fill in the reversed charactrs result
    for (int i = strlength - 1; i >= 0; --i) {
                                     // ^^ Prefer the prefix increment operator 
                                     // to avoid unnecessary copies         
        tempStr[index] = string[i];
             // ^^^^^ Use this index to fill in tempStr[index]
        cout << tempStr[index]; 
        ++index;
    }
    cout << endl;

    // tempStr[strlength] = 0;
    cout << "reversed word: " << tempStr << endl;
    return tempStr;
}

---

void string_reverse1(const char* string) {
    char* tempChar = string_reverse2(string);
    cout << tempChar << endl;
    // Don't forget to finally release the memory allocated in string_reverse2()
    delete [] tempChar;
}

---

int main() {
    string_reverse1("Hello");
    return 0;
}

---

输出：

the word to reverse: Hello

olleH
reversed word: olleH

我一直在上面的代码示例的注释中指出了必要的修复。