如何反轉字符串中的單詞順序（不是字母）？

Question

我將如何去扭轉字符串中的單詞順序？我試過，但它不工作：

string sen = "Go over there"; 
reverse(sen.begin(), sen.end()); 

但這種反轉整個字符串，但不保留詞語的正確的順序。我如何才能顛倒字符串中的單詞順序？

Answer 1

如果字符串中的單詞用空格分開，你可以使用一個string.find()循環while裏面找到斷裂，然後用string.substr()輸出的話到vector。然後你可以簡單地向後閱讀vector。

Answer 2

Live Example

如果使用C++ 11，sen.pop_back()擺脫過去的空間，否則，你可以爲其他的例子退房Remove last character from C++ string。其次，我們不使用std::reverse(output.begin(), output.end())，而是使用反向迭代器rbegin()和rend()。 for循環可以明顯改進，但它可以完成這項工作。

#include <sstream> 
#include <iterator> 
#include <algorithm> 
#include <iostream> 

using namespace std; 
int main(int argc, char *argv[]) { 
    std::vector<std::string> output; 
    std::string sen = "Go over there"; 
    std::string word = ""; 
    unsigned int len = 0; 
    for (const auto& c : sen) { 
     ++len; 
     if (c == ' ' || len == sen.size()) { 
      if (len == sen.size()) 
       word += c; 
      output.push_back(word); 
      word = ""; 
     } 
     if (c != ' ') 
      word += c; 
    } 
    std::ostringstream oss; 
    std::copy(output.rbegin(), output.rend(), std::ostream_iterator<std::string>(oss, " ")); 
    sen = oss.str(); 
    sen.pop_back(); // Get rid of last space, C++11 only 
    std::cout << sen; 
} 

Answer 3

我已經寫了很多這樣的字符串函數之前：

// Make copy of this original if you don't wish to destroy in the process 
string sen = "Go over there"; 

// string that will become your reversed string 
string newStr = new string(); 

// A temp variable that will hold the current position of the last separator character 
int aChar  = -1; 

//////////////////////////////////////////////////////////////////////////////////////// 
// You may want to delete pre and post spaces here 
//////////////////////////////////////////////////////////////////////////////////////// 

// Loop through the entire string until the original is empty 
while(sen.length > 0){ 
    // Find the last separator character (in your case a space) within the string 
    aChar = sen.find_last_of(" "); 

    // Append the word created from one char forward of the last found separator char 
    // to the end of the CURRENT version of the original string 
    newStr += sen.substr(aChar + 1, sen.length - aChar - 1); 

    // Store a new version of the original string that is the SUBSTRING from beginning (char 0) 
    // to one char before the last found separator character 
    sen  = sen.substr(0, aChar - 1); 

    // Need to add the space between the words, but only if the new substring is not empty 
    if(sen.length > 0) newStr += " "; 
} 

我還沒有測試此代碼，但如果API的工作，他們的目的的方式，算法這應該工作。

作爲一個API，這可能看起來像如下

string reverse(string inStr){ 
    // Make copy of the original so we don't destroy it in the process 
    string sen = inStr.copy(); 

    // string that will become your reversed string 
    string newStr(); 

    // A temp variable that will hold the current position of the last separator character 
    int aChar  = -1; 

    //////////////////////////////////////////////////////////////////////////////////////// 
    // You may want to delete pre and post spaces here 
    //////////////////////////////////////////////////////////////////////////////////////// 

    // Loop through the entire string until the original is empty 
    while(sen.length > 0){ 
     // Find the last separator character (in your case a space) within the string 
     aChar = sen.find_last_of(" "); 

     // Append the word created from one char forward of the last found separator char 
     // to the end of the CURRENT version of the original string 
     newStr += sen.substr(aChar + 1, sen.length - aChar - 1); 

     // Store a new version of the original string that is the SUBSTRING from beginning 
     // (char 0) to one char before the last found separator character 
     sen  = sen.substr(0, aChar - 1); 

     // Need to add the space between the words, but only if the new substring is not empty 
     if(sen.length > 0) newStr += " "; 
    } 

    return newStr; 
} 

int main(int argc, char *argv[]){ 
    string sen = "Go over there"; 
    string rev = reverse(sen); 
}