如何使用数组查找字符串中的字母C++

Question

我试图解密一个句子。对于找到的每个单词，我都想将其添加到计数器中。我有一个嵌套for循环，当用户键入句子时，一个for循环将循环遍历句子（int i = 0），另一个（int j = 0）循环遍历数组，并且当它们找到相应的字母。我认为我所做的是有道理的，但由于某种原因，它不起作用。这里有一段代码处理本节。预先感谢您:)

#include <iostream> 
#include <string> 
#include <cctype> 

using namespace std; 
string alphebet[26] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"}; 

string sentence; 
cin >> sentence; 
for(int i = 0; i < sentence.length(); i++){ 
    for(int j = 0; j < alphebet; j++){ 
     if (sentence[i] == alphebet[j]){ 
      counter_letters = counter_letters + 1; 
     } 
    } 
} 

Answer 1

首先改变你的alphebet的字符数组像这样的char alphabet[26]。然后，您需要使用getline(cin, sentence)来获取像“Hello World”这样的整行输入，而cin << sentence只能得到第一个单词。接下来，您需要将字符串转换为大写，以便稍后与您的alphebet匹配，请使用transform(sentence.begin(), sentence.end(), sentence.begin(), ::toupper);执行此操作。之后，一定要初始化变量counter_letters。作为一个附注，你不需要做counter_letters = counter_letters + 1;你可以做counter_letters += 1;或counter_letters++;或++counter_letters;。

#include <iostream> 
#include <string> 
#include <cctype> 
#include <algorithm> 

using namespace std; 
int main() { 
    char alphebet[26] = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'}; 

    string sentence; 
    getline(cin,sentence); 
    transform(sentence.begin(), sentence.end(), sentence.begin(), ::toupper); 

    int counter_letters = 0; 
    for(int i = 0; i < sentence.length(); i++){ 
     for(int j = 0; j < 26; j++){ 
      if (sentence[i] == alphebet[j]){ 
       counter_letters++; 
      } 
     } 
    } 
    cout << counter_letters << endl; 
} 

Answer 2

我不确定您的问题在这里，但有一个提议是，您可能会在输入中输入空格。 CIN亘古不变的阅读空间，所以如果这不是问题，你的代码可能无法正常工作

，请参阅以下链接中的字符串来算大写字母，小写字母 How to code a C++ program which counts the number of uppercase letters, lowercase letters and integers in an inputted string?