为什么我的代码中出现分段错误？

Question

I keep getting segmentation fault, how can I fix that. I tryed more variants but I get segmentation fault everytime when I am using if statements. My code is something similar with this:

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

int main()
{
    int i;
    char *sentence[300];
    fgets(*sentence,300,stdin);
    int length=strlen(*sentence);
    for(i=0;i<length;i++){
        if(sentence[i]=="a")
            printf("qwer");
        else if(sentence[i]=="b")
            printf("asdf");
        else if(sentence[i]=="c")
            printf("zxcv");
//      ...
    }
    return 0;
}

Answer 1

The first thing you're doing wrong is this:

char *sentence[300];

It looks like you're trying to create a buffer of 300 characters, but what you're really doing is creating an array of 300 character pointers. Change that to:

char sentence[300];

Then you want to change this:

fgets(*sentence,300,stdin);

to

fgets(sentence,sizeof(sentence),stdin);

Then you want to change

int length=strlen(*sentence);

to

int length=strlen(sentence);

You need to have a good understanding of how strings work in C. If you haven't read a good introductory book for C, start there. C is not something you're going to pick up by just reading random pages on the web and StackOverflow.