英文:
Sorting algorithm works for C-array but not works for std::span
问题
这个问题发生在我正在编写插入排序算法时。我尝试实现一个适用于C++20的std::span版本，但它抛出了"std::span索引超出范围"的错误。所以我将它改成了"C数组"，相同的代码可以正常工作。我不知道问题出在哪里。P.S我的平台是Windows 10，我正在使用Visual Studio 2022。
这是std::span版本。
template <typename Ty>void insertion_sort(std::span<Ty> arr) {long long size = arr.size();// 从第二个元素到第n个元素for (long long i = 1; i < size; ++i) {Ty key = arr[i];long long j = i - 1;// 直到第一个元素。for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];// 将key放入正确的位置。arr[j + 1] = key;}}
然而，如果我将std::span更改为C数组，如下所示，它可以正常工作。
template <typename Ty>void insertion_sort(Ty* arr, std::size_t size) {// 从第二个元素到第n个元素for (long long i = 1; i < size; ++i) {Ty key = arr[i];long long j = i - 1;// 直到第一个元素。for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];// 将key放入正确的位置。arr[j + 1] = key;}}
如果有人能帮助我解决这个问题，我将不胜感激！
英文:
This problem happens when I am working on a insertion_sort algorithm.
I tried to implement a version for C++20's std::span but it throws a "std::span index out of range" So I turned it to "C-array" the same code works fine.
I don't know where is the problem. P.S My platform is windows10 and I'm using VisualStudio2022
This is the std::span version.
template <typename Ty>void insertion_sort(std::span<Ty> arr) {long long size = arr.size();// From the 2nd element to the nth elementfor (long long i = 1; i < size; ++i) {Ty key = arr[i];long long j = i - 1;// Until the first element.for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];// Place key into the right position.arr[j + 1] = key;}}
However if I change std::span to C-array, like below, it works fine.
template <typename Ty>void insertion_sort(Ty* arr, std::size_t size) {// From the 2nd element to the nth elementfor (long long i = 1; i < size; ++i) {Ty key = arr[i];long long j = i - 1;// Until the first element.for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];// Place key into the right position.arr[j + 1] = key;}}
I'll be glad if someone can help me fix this problem!
答案1
得分: 2
以下是翻译好的部分：
在for循环中的条件
for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];
是错误的。您需要交换逻辑AND运算符的操作数
for (; j >= 0 && arr[j] > key; --j)arr[j + 1] = arr[j];
否则，表达式arr[j]的索引可以等于-1。
英文:
The condition in the for loop
for (; arr[j] > key && j >= 0; --j)arr[j + 1] = arr[j];
is wrong. You need to exchange the operands of the logical AND operator
for (; j >= 0 && arr[j] > key; --j)arr[j + 1] = arr[j];
Otherwise the index of the expression arr[j] can be equal to -1.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论