在strtok（）-C的輸出上使用strcmp（）

Question

我是C語言的新手，我正在嘗試編寫一個程序，該程序使用兩個字符串文字，在第一個字符串中找到最長的單詞，然后將其與第二個字符串進行比較。 如果第二個字符串（稱為“期望”）的確與第一個字符串相等，則顯示成功消息，否則，將輸出實際最長的單詞，預期的字符串和原始字符串。

這里還有許多其他類似問題的帖子，但歸結為\\n或\\0;丟失\\0; 據我了解， strtok() \\0並且由於我使用的是硬編碼文字，因此我確定不會出現換行符，就像讀取輸入一樣。

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

char* currentTok;
static const char* result;
static char* longestTok;

static int testsExecuted = 0;
static int testsFailed = 0;

void testLongestWord();
const char* longestWord();
int totalLength();
int charLength();

int main(int argc, char *argv[]) {
    printf("Testing typical cases, including punctuation\n");
    testLongestWord("the quick brown foxes jumped over the lazy dogs", "jumped");
    //There are other examples, some of which fail, and others don't, though I don't see a pattern

    printf("\nTotal number of tests executed: %d\n",testsExecuted);
    printf("Number of tests passed:         %d\n",(testsExecuted - testsFailed));
    printf("Number of tests failed:         %d\n",testsFailed);
}

//tests words, prints success/failure message
void testLongestWord(char* line, char* expected){
    result = longestWord(line, totalLength(line));
    if (strncmp(result, expected,charLength(expected)-1)||totalLength(expected)==0){//the problem spot
        printf("Passed: '%s' from '%s'\n",expected, line);
    } else {
        printf("FAILED: '%s' instead of '%s' from '%s'\n",result, expected, line);
        testsFailed++;
    }
    testsExecuted++;
}

//finds longest word in string
const char *longestWord(char* string, int size){
    char tempString[size+10];//extra room to be safe
    strcpy(tempString,string);
    currentTok = strtok(tempString,"=-#$?%!'' ");
    longestTok = "\0";
    while (currentTok != NULL){
        if (charLength(currentTok)>charLength(longestTok)){
            longestTok = currentTok;
        }
        currentTok = strtok(NULL,"=-#$?%!'' ");
    }

    return longestTok;
}

int totalLength(const char* string) {
    int counter = 0;

    while(*(string+counter)) {
        counter++;
    }
    return counter;
}

int charLength(const char* string) {
    int counter = 0;
    int numChars = 0;

    while(*(string+counter)) {
        if (isalpha(*(string+counter))){
            numChars++;
        }
        counter++;
    }
    return numChars;
}

問題是它返回：

FAILED: 'jumped' instead of 'jumped' from 'the quick brown foxes jumped over the lazy dogs'

顯然，字符串是相等的，並且我已經做了其他測試以確保它們的長度相同，具有\\0 ...，但仍然失敗。

Answer 1

您正在調用strncmp() ，該字符串在相等的字符串上返回零，但是您正在布爾值上下文中對它進行求值，其中零為false，因此它屬於else分支。

另外，考慮使用strlen()找出字符串的長度。