c - 在 strtok() -C 的输出上使用 strcmp()

Question

我是 C 的新手，我正在尝试编写一个程序，它接受两个字符串文字，在第一个字符串中找到最长的单词，并将其与第二个字符串进行比较。如果第二个字符串(称为“expected”)确实等于第一个，它会打印一条成功消息，如果不是，它会打印实际最长的单词、预期的字符串和原始字符串。

这里有许多其他帖子也有类似的问题，但据我所知，这些归结为添加的 \n 或缺少的 \0;，strtok() 添加 \0 并且因为我使用的是硬编码文字，所以我确信没有尾随换行符，就像读取输入的情况一样。

#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;
}

问题是它返回:

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

很明显，字符串是相等的，我已经做了其他测试以确保它们的长度相同，有 \0...但它仍然失败。

Answer 1

您正在调用 strncmp()，它在相同的字符串上返回零，但您正在 bool 上下文中对其进行评估，其中零为假，因此它落入 else 分支。

此外，考虑使用 strlen() 来找出字符串的长度。