指向字符串C [英] Pointers to string C

问题描述

尝试编写功能，如果中字每个字母出现在S返回1。
例如：


  

containsLetters1（this_is_a_long_string，气）返回1

  
  

containsLetters1（this_is_a_longstring，嘎斯）返回0

  
  

containsLetters1（你好，P）返回0

不明白为什么它不正确的：

 的#include＆LT;＆stdio.h中GT;
＃包括LT＆;＆string.h中GT;
＃定义MAX_STRING 100INT containsLetters1（字符* S，字符*字）
{
INT J，I，标志;
长LEN;
LEN = strlen的（字）;对于（i = 0; I＆LT; = LEN;我++）{
    标志= 0;
    为（J = 0; J＆LT; MAX_STRING; J ++）{
        如果（字== S）{
            标志= 1;
            字++;
            小号++;
            打破;
        }
        小号++;    }
    如果（标志== 0）{
        打破;
    }
}
返回标志;
}诠释主（）{
    字符字符串1 [MAX_STRING] 1，字符串[MAX_STRING]的printf（请输入2字符串containsLetters1 \\ n）;scanf函数（％s％S，字符串1，字符串）;的printf（从containsLetters1返回值是：％d个\\ N，containsLetters1（字符串1，字符串））; 返回0;
 

解决方案

尝试这些：

1. 为（i = 0; I＆LT; LEN，我++）... （使用＆lt;而非＆LT; =，否则你会采取一个额外的字符）;


2. 如果（字== S）应如果（*字== * S）（你比较存储在尖的位置，而不是指针）字符;


3. 指针小号的进步，但它应该得到回字取值，达到其目的，即在 S的开始 - = LEN 在为（J = ...）;


4. 取值++ 字++ 后是不需要的，你按相同的量超前的指针，你是否未找到匹配;


5. 标志应与申报1时初始化。

trying to write function that returns 1 if every letter in "word" appears in "s". for example: 

containsLetters1("this_is_a_long_string","gas") returns 1

containsLetters1("this_is_a_longstring","gaz") returns 0

containsLetters1("hello","p") returns 0

Can't understand why its not right:

#include <stdio.h> 
#include <string.h>
#define MAX_STRING 100

int containsLetters1(char *s, char *word)
{
int j,i, flag;
long len;
len=strlen(word);

for (i=0; i<=len; i++) {
    flag=0;
    for (j=0; j<MAX_STRING; j++) {
        if (word==s) {
            flag=1;
            word++;
            s++;
            break;
        }
        s++;

    }
    if (flag==0) {
        break;
    }
}
return flag;
}

int main() {
    char string1[MAX_STRING] , string2[MAX_STRING] ;

printf("Enter 2 strings for containsLetters1\n");

scanf ("%s %s", string1, string2);

printf("Return value from containsLetters1 is: %d\n",containsLetters1(string1,string2));

 return 0; 

解决方案

Try these:

1. for (i=0; i < len; i++)... (use < instead of <=, since otherwise you would take one additional character);
2. if (word==s) should be if (*word==*s) (you compare characters stored at the pointed locations, not pointers);
3. Pointer s advances, but it should get back to the start of the word s, after reaching its end, i.e. s -= len after the for (j=...);
4. s++ after word++ is not needed, you advance the pointer by the same amount, whether or not you found a match;
5. flag should be initialized with 1 when declared.

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