英文:
Expression must have a constant value error when creating an array C++
问题
抱歉，你的代码中存在一些问题，我会帮你指出并提供一些修复建议。以下是翻译好的部分：
Good day. Faced an error "Expression must have a constant value" when creating an array. Find this question <https://stackoverflow.com/questions/9219712/c-array-expression-must-have-a constant-value#>, but these tips didn't solve the problem. Please help and I'm sorry for such requests, I just started to learn C ++Code:#include <iostream>#include <math.h>#include <cstdlib>#include <string>#include <sstream>#include <conio.h>#include <random>int main(){int userInput = 0, sumEvenIndexElements = 0, sumElementsBetweenZero = 0;bool checkZeroElements = false;std::cout << "Write array length:" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;int *numbers = new int[lengthOfArray]; // 使用new分配动态数组std::default_random_engine generator;std::uniform_int_distribution<int> distribution(-10, 10);for (int index = 0; index < lengthOfArray; index++){numbers[index] = distribution(generator); // 存储随机数而不是分配新的int数组std::cout << numbers[index] << std::endl;if (index % 2 == 0){sumEvenIndexElements += numbers[index]; // 累加偶数索引元素}}std::cout << "Sum even index elements: " << sumEvenIndexElements << std::endl;for (int index = 0; index < lengthOfArray; index++){if (numbers[index] == 0){checkZeroElements = !checkZeroElements;}if (checkZeroElements){sumElementsBetweenZero += numbers[index]; // 累加两个零之间的元素}}if (!checkZeroElements){std::cout << "Sorry, array has less than two zero elements.";}else{std::cout << "Sum elements between two zeros: " << sumElementsBetweenZero << std::endl;}delete[] numbers; // 释放动态分配的数组内存return 0;}
请注意，我已经做了一些修改来修复代码中的错误。希望这对你有所帮助。如果你有任何其他问题，请随时提问。
英文:
Good day. Faced an error "Expression must have a constant value" when creating an array. Find this question <https://stackoverflow.com/questions/9219712/c-array-expression-must-have-a-constant-value#>, but these tips didn’t solve the problem. Please help and I'm sorry for such requests, I just started to learn C ++
Code:
#include <iostream>#include <math.h>#include <cstdlib>#include <string>#include <sstream>#include <conio.h>#include <random>int main(){int userInput = 0, sumEvenIndexElements = 0, sumElementsBeetwenZero = 0;bool checkZeroElements = false;std::cout << "Write array length:" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;int numbers [lengthOfArray];std::default_random_engine generator;std::uniform_int_distribution<int> distribution(-10, 10);for (int index = 0; index < lengthOfArray; index++){numbers[index] = new int[distribution(generator)];std::cout << numbers << std::endl;if (index % 2 == 0){sumEvenIndexElements += *numbers[index];}}std::cout << "Sum even index elements: " << sumEvenIndexElements << std::endl;for (int index = 0; index < lengthOfArray; index++){numbers[index] = new int[distribution(generator)];if (numbers[index] == 0){checkZeroElements = !checkZeroElements;}if (checkZeroElements){sumElementsBeetwenZero += *numbers[index];}}if (checkZeroElements){std::cout << "Sorry, array have less than two zero elements.";}else{std::cout << "Sum even index elements: " << sumEvenIndexElements << std::endl;}}
答案1
得分: 1
lengthOfArray 是一个常量变量，它的值在初始化之后不会在运行时改变。
但它的值 - userInput 不是一个常量，它依赖于运行时用户的输入。正如在这里所指出的
常量值 是一个明确的数字或字符，例如1或0.5或'c'。
建议您使用std::vector而不是数组，如Paul Evans的答案中所建议的，或者为lengthOfArray分配一个适当的常量值，该值将在编译时已知，例如：
const int lengthOfArray = 10;
英文:
lengthOfArray is a constant variable, it's value would not be chagned during runtime after initialization.
But it's value - userInput is not a constant, it dependes on runtime user input. As pointed here
> A constant value is an explicit number or character such as 1 or 0.5
> or ‘c’.
You should use std::vector instead of an array, as suggested in Paul Evans's answer, or assign a proper constant value to the lengthOfArray , which will be known at the time of compilation, e.g.:
const int lengthOfArray = 10;
答案2
得分: 0
Your code:
std::cout << "写入数组长度：" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;int numbers[lengthOfArray];
无法编译成功，根据你所遇到的编译器错误。
std::vector 更容易使用：
std::cout << "写入数组长度：" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;std::vector<int> numbers(lengthOfArray, 0);
将创建一个长度为lengthOfArray的std::vector，并且所有元素都初始化为0。
英文:
Your code:
std::cout << "Write array length:" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;int numbers [lengthOfArray];
won't work as per the compiler error you're getting.
std::vector plays a lot nicer:
std::cout << "Write array length:" << std::endl;std::cin >> userInput;const int lengthOfArray = userInput;std::vector<int> numbers(lengthOfArray, 0);
will create a std::vector of int of length lengthOfArray all initialised to 0.
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