我需要帮助修复试图在字符串中查找子字符串的代码

I need help fixing a code trying to find substring in a string

本文关键字：字符串 查找 代码 帮助 复试      更新时间：2024-04-28

我正在尝试创建一个新字符串并将月份名称写入其中，然后使用它来检查我是否已经将月份名称写到文件中。这是我试图修复的代码：

void writeToFile(RainStruct rainPerMonth[], int monthsInYear)
{
// Create string variable
string month;

// Create and open file
fstream rainFile("scramble.txt", ios::out);

// Write into file, goes through each structure and writes it
for (int count = 0; count < 11; count++)
{
// Set random number variable
int randNum = rand() % 12;

// Set string variable month to different random month names
month += rainPerMonth[randNum].monthNames;

// Call to checkMonth
if (checkMonth(rainPerMonth, monthsInYear, randNum, month))
{
// Write months in random order to file
rainFile << rainPerMonth[randNum].monthNames << " had " << rainPerMonth[randNum].monthRain    << " inches.n";
}
}

// Close, reopen, truncate, and close file again
rainFile.close();
rainFile.open("scramble.txt", ios::trunc);
rainFile.close();
}
bool checkMonth(RainStruct rainPerMonth[], int monthsInYear, int randNum, string month)
{
size_t pos = month.find(rainPerMonth[randNum].monthNames);
if(pos != string::npos)
{
return true;
}
else
{
return false;
}
}

它最终会打印两次某些月份，而不是打印所有月份。我需要更改什么来修复它，以随机顺序将所有月份写入文件(附上每月的降雨量(？这是我的完整代码：https://onlinegdb.com/ry6yO4a4_赋值的规范是，我必须使用一个字符串变量来搜索字符串中的子字符串，然后检查它是否已经存在，然后将月份写入文件。他说我必须使用随机生成器，不能硬编码。这是他给我们的提示：http://www.cplusplus.com/reference/string/string/substr/

您可以使用shuffle()函数引用中的示例来创建一个月份索引的混洗列表，然后将其写入文件。rand()不保证唯一索引，因此它可能返回[0, 11]之间的任何数字，甚至可能重复它们。

#include <algorithm>
#include <array>
#include <iostream>
#include <random>

void print(const auto& a) {
for (const auto e : a) { std::cout << e << ' '; }
std::cout << "n";
}

int main()
{
std::array a{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
print(a);

std::random_device rd;
std::mt19937 gen{rd()};

for (int i{}; i != 3; ++i) {
std::ranges::shuffle(a, gen);
print(a);
}
//Then just use a[0], a[1]...as the index to rainPerMonth[] and write it out to file
}

输出：

0 1 2 3 4 5 6 7 8 9 10 11 
10 4 6 7 8 11 2 5 9 1 3 0 
0 5 7 4 2 8 11 9 6 1 10 3 
10 8 5 7 9 4 2 6 11 1 3 0

这在不添加更多依赖项的情况下充分利用了您的需求(尽管std的向量和数组非常好(：

struct RainStruct{
RainStruct(std::string monthNames, int monthRain){
this->monthNames = monthNames;
this->monthRain = monthRain;
}
std::string monthNames;
int monthRain;
};

// Shuffle array
void shuffle_array(int arr[], int n)
{

// To obtain a time-based seed
unsigned seed = 0;

// Shuffling our array
shuffle(arr, arr + n,
std::default_random_engine(seed));

// Printing our array
for (int i = 0; i < n; ++i)
std::cout << arr[i] << " ";
std::cout << std::endl;  // you wont need this
}
void writeToFile(RainStruct rainPerMonth[], int monthsInYear)
{
// Create integers array
int nums[12] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
shuffle_array(nums, 12);
for (int count = 0; count < 12; count++)
{
// Set random number variable
int randNum = nums[count]-1;
std::cout << rainPerMonth[randNum].monthNames << " had " << 
rainPerMonth[randNum].monthRain    << " inches.n";
}
}

int main()
{  

RainStruct structSample[12] = { RainStruct("Jan", 1) , 
RainStruct("Feb", 2) , 
RainStruct("Mar", 3) , 
RainStruct("Apr", 4) , 
RainStruct("May", 5) , 
RainStruct("Jun", 6) , 
RainStruct("Jul", 7) , 
RainStruct("Agu", 8) , 
RainStruct("Sep", 9) , 
RainStruct("Oct", 10) , 
RainStruct("Nov", 11) , 
RainStruct("Dec", 12) , 
}; 
writeToFile(structSample, 12);
}

输出：

3 8 11 7 12 1 5 10 6 4 2 9 
Mar had 3 inches.
Agu had 8 inches.
Nov had 11 inches.
Jul had 7 inches.
Dec had 12 inches.
Jan had 1 inches.
May had 5 inches.
Oct had 10 inches.
Jun had 6 inches.
Apr had 4 inches.
Feb had 2 inches.
Sep had 9 inches.

您可以使用您的方法来编写文件

问题是，当你要求一堆随机数时，随机数生成器会生成两次相同的数字。随机抽取12个数字，会发现有些数字缺失，有些数字重复。

要解决这个问题，您需要首先以随机顺序构建一个月份编号数组，确保所有月份都在其中，并且没有重复。否则，你会看到你提到的效果。

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