用 C 中的另一个词替换字符串中的一个词

问题描述

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

int main(void){
    char sen[100];
    char word[30];
    char rep[30];
    printf("Enter a sentence> ");
    gets(sen);
    printf("Enter a word to compare> ");
    gets(word);
    printf("Enter a word to replace with> ");
    gets(rep);
    int sen_len = strlen(sen);
    int word_len = strlen(word);
    char temp[30];
    char retSen[100];
    char rest[70];
    int i;
    int y=0;
    for(i=0; i<sen_len; i++){
        //Loop through characters in sentence until you reach a whitespace. ie,extract a word and put it in temp.
        if(sen[i] == ' '){
            //Compare the word with target word
            if(!strcmp(temp,word)){
                //In case of match,copy the part upto but not including the matching word and put it in the final string (retSen)
                strncpy(retSen,sen,sen_len-i);
            }else{
                //Clear temp and skip to next iteration
                y=0;
                temp[0] = '\0';
                continue;
            }
        }
        y++;
        //Repeatedly populate y with a word from sen
        temp[y] = sen[i];
    }
    int x=0;
    for(int j=i; j<sen_len; j++){
        //Populate another char array with the rest of the sentence after the matching word.
        rest[x] = sen[j];
    }
    //Join the part upto the matching word with the replacing word.
    strcat(retSen,rep);
    //Then join the rest of the sentence after the matching word to make the full string with the matching word replaced.
    strcat(retSen,rest);
    puts(retSen);
    return 0;
}

我正在尝试制作一个程序，它需要一个句子、一个要替换的目标词和另一个替换目标的词。此代码不起作用。由于某种原因，它只是打印替换词 + 'a'。如何修复此代码？

解决方法

在 C 中，您需要构建自己的字符串替换函数。我认为您的用例可以很好地利用 strtok()、strcat() 和 strncat() 函数，

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

// Prototypes:
int searchForWord( const char * haystack,const char * needle );
char * searchAndReplace( const char * haystack,const char * needle,const char * newNeedle );

/**
 * main
 */
int main()
{
    const char * sentence = "The quick brown fox jumped over the lazy dog." ;
    const char * wordToReplace = "fox" ;
    const char * replacementWord = "turtle" ; 

    // ... Search and replace...
    char * newSentence = searchAndReplace( sentence,wordToReplace,replacementWord ) ;
    
    // ... Show the result
    if ( newSentence ) {
        printf( "%s\n",newSentence ) ;
        free( newSentence ) ;
    } else {
        printf( "%s\n",sentence ) ;
    }

    return 0;
}

/**
 * Take a sentence,and replace the first occurrence of a word with another word.
 * 
 * Parameters:
 * haystack: the original sentence
 * needle: the word to search and replace
 * newNeed: the word to use as replacement
 * 
 * Returns:
 * A new modified string,or NULL if the word was never found.
 * 
 * Note: 
 * The result is dynamically allocated so it mut be freed once no longer needed.
 */
char * searchAndReplace( const char * haystack,const char * newNeedle ) 
{
    // ... Is the word in the sentence?
    int offset = searchForWord( haystack,needle ) ;
    if ( offset < 0 ) {
        fprintf( stderr,"searchAndReplace: %s not found in the given setence\n",needle );
        return NULL;
    }
    
    // ... From the found offset,determine the end offset of the word
    int offsetEnd = offset + strlen(needle);
    
    // ... Create a new buffer that will contain the modified sentence
    int newSize = strlen( haystack ) - strlen( needle ) + strlen( newNeedle ) + 1 ;
    char * result = (char*)malloc( newSize * sizeof(char) ) ;
    
    // ... Initialize the new buffer to a zero-length string
    result[ 0 ] = '\0';
    
    // ... Build the new sentence: first part (before the found word)
    if ( offset > 0 ) {
        strncat( result,haystack,offset) ;
    }
    
    // ... Build the new sentence: replaced word
    strcat( result,newNeedle ) ;
    
    // ... Build the new sentence: last part
    strncat( result,&haystack[ offsetEnd ],strlen(&haystack[ offsetEnd ]) ) ;
    
    return result ;
}

/**
 * Find the location of a word in a sentence,assuming words are whitespace-
 * delimited.
 * 
 * Returns: offset of the word in the sentence,or -1 if not found
 */
int searchForWord( const char * haystack,const char * needle ) 
{
    int result = -1 ;
    
    const char * delims = " \n\r\t" ; // whitespaces
    
    // ... Get a copy of haystack,as strtok() will alter it
    char * copy = strdup(haystack) ;
    
    // ... For each word in the sentence
    for ( char *p = strtok( copy,delims ); p != NULL; p = strtok( NULL,delims ) ) {
        // ... If the word matches what we're looking for
        if ( strcmp( p,needle ) == 0 ) {
            // ... Set the offset in the sentence
            result = p - &copy[ 0 ] ;

            // ... We're done searching
            break ;
        }
    }
    
    // .... Avoid memory leaks
    free( copy ) ;
    
    // ... Return whatever we found (or not)
    return result ;
}