使用C反向字符串比較使用C

Question

我剛剛編譯這個程序，但它似乎不工作。

我應該做的是制定一個程序，確定一個單詞是否是迴文（前後相同的單詞，例如「賽車」或「眼睛」）。

它也應該忽略大小寫字母（例如Racecar或eYe）。這是我到目前爲止有：

int main() 

    char word[21],reverse[21]; 
    printf("Type a word and I will tell you if it is a Palindrome: "); 
    fgets(word,21,stdin); 
    puts(""); 
    printf("The word that you typed is: %s \n",word); 
    strcpy(reverse,word); 
    strrev(reverse); 
    if((strcmp(reverse,word))==0) 
    printf("This word is a palindrome"); 
    else 
    printf("This word is NOT a palindrome"); 

    return 0; 
} 

Answer 1

fgets()存儲換行符到提供的緩衝區，如果遇到一個。當您輸入一個單詞並按回車鍵時，「輸入」會產生一個換行符，並將其存儲在緩衝區中。當你反轉字符串時，換行字符將成爲反轉的一部分，因此，你永遠不會得到肯定的結果。此外，爲了確保比較可以不區分大小寫，可以先將整個單詞轉換爲小寫（或大寫）。

#include <ctype.h> 
#include <stdio.h> 
#include <string.h> 

int main() 
{ 
    char word[21] = {0}, reverse[21]; 

    printf("Type a word and I will tell you if it is a Palindrome: "); 
    fgets(word,21,stdin); 

    // remove linefeed character if there is one 
    size_t len = strlen(word); 
    if (len > 0 && word[len - 1] == '\n') 
    { 
     word[len - 1] = '\0'; 
     len--; 
    } 

    // convert string to lowercase 
    for (size_t i = 0; i < len; i++) 
     word[i] = tolower(word[i]); 

    puts(""); 
    printf("The word that you typed is: %s \n",word); 

    strcpy(reverse,word); 
    strrev(reverse); 

    if((strcmp(reverse,word))==0) 
     printf("This word is a palindrome"); 
    else 
     printf("This word is NOT a palindrome"); 

    return 0; 
} 

Answer 2

你不需要字符串逆向檢查它是否是一個迴文，也strrev是不是在C標準的功能。您可以從單詞的開頭和結尾處進行檢查：

char word[21]; 
printf("Type a word and I will tell you if it is a Palindrome: "); 
fscanf(stdin, "%s", word); 
puts(""); 
printf("The word that you typed is: %s \n",word); 

size_t len = strlen(word); 
int s; 
bool palindrome = true; 
for (s = 0; s < len/2; s++) { 
    if (tolower(word[s]) != tolower(word[len-1-s])) { 
     palindrome = false; 
     break; 
    } 
} 
if(palindrome) 
    printf("This word is a palindrome"); 
else 
    printf("This word is NOT a palindrome"); 

這節省了空間和時間。

Answer 3

• 試試這個簡單的代碼：

#include <stdio.h> 
#include <string.h> 

int main() 
{ 
    char word[21] = {0}, reverse[21] = {0}; 
    int len; 
    printf("Type a word and I will tell you if it is a Palindrome: "); 
    fgets(word,21,stdin); 

    len = strlen(word); 

    // convert string to lowercase and remove '\n' feed problem if any 
    for (int i = 0; i < len ; i++) 
    { 
    if(word[i] != '\n') 
    word[i] = tolower(word[i]); 
    } 
    word[i] = '\0'; 

    puts(""); 
    printf("The word that you typed is: %s \n",word); 

    strcpy(reverse,word); 
    strrev(reverse); 

    if((strcmp(reverse,word))==0) 
     printf("This word is a palindrome"); 
    else 
     printf("This word is NOT a palindrome"); 

    return 0; 

Answer 4

與fgets，也使\ n在字符串的結尾。 所以，正確的代碼將是這樣的：

int main() 
{ 

    char word[21],reverse[21]; 
    printf("Type a word and I will tell you if it is a Palindrome: "); 
    fgets(word,21,stdin); /// Actually it saves: "123\n" 
    word[strlen(word)-1] = '\0'; 
    puts(""); 
    printf("The word that you typed is: %s \n",word); 
    strcpy(reverse,word); 
    strrev(reverse); 
    if((strcmp(reverse,word))==0) 
    printf("This word is a palindrome"); 
    else 
    printf("This word is NOT a palindrome"); 

    return 0; 
}