I really don't know how to explain it. Please bear with me.
I try to pass the 2 dimensional array into a function string[][]
, and in that function I going to create a pointer which point to the array I passed in. I will do compare of element in string[][]
//From main
char string[3][3] = {"cat","dog","bat"};
//From function
declare a pointer which points to string;
if (strcpm(string[1],string[2]) == 1)
{
pointer[1] value set to address of string[2];
pointer[2] value set to address of string[1]
}
printf("%s", *(pointer));
I don't want to modify string[3][3]
, then the function would quit the function without return anything
I have the idea, but I don't know how to declare pointer
, please help me. Thanks! Visualize
In main In function
string ptr
cat 1000
dog 1008
bat 1012
Do compare
dog > bat
ptr[3] = address of dog;
ptr[2] = addess of bat;
printf("%s", *(ptr+1);
printf("%s", *(ptr+2);
quit function, return nothing
in C, strings are represented as an array of characters. This is represented in two normal ways, char* identifier
and char identifier[]
. A 2 dimensional Array is declared as a pointer to the string. So, it can be written as
char **strArray1
char *strArray2[]
char strArray3[][]
Each has different implications, that I won't get into here as it's pedantic.
To answer your question as literally as I can, you can write the code in your post as
int main (void) {
char * strArray[2] = { "This is a String", "This is a String too" };
if (strcmp(strArray[0], strArray[1]) == 0) {
...
}
return 0;
}
For a function to accept an array of strings (not an array of pointers to strings, which is different):
void func(size_t rows, size_t cols, char strings[rows][cols])
{
char const *pointers[rows];
// Initialize each pointer to point to each row
for (size_t i = 0; i < rows; ++i)
pointers[i] = &strings[i][0];
// here you can manipulate the pointers, e.g. bubble sort them
printf("%s\n", pointers[0]);
}
Calling this function:
int main()
{
char stuff[4][20] = { "cat", "dog", "snuffleupagus", "horse" };
func(4, 20, stuff);
}
Pro tip: you can compute array dimensions instead of using magic numbers:
#define LENGTH_OF(array) ( sizeof(array) / sizeof((array)[0]) )
char stuff[][20] = { "cat", "dog", "snuffleupagus", "horse" };
func( LENGTH_OF(stuff), LENGTH_OF(stuff[0]), stuff );
As noted in comments, be careful about the second dimension ( 20
in my case). C permits an array of char to be initialized with a string of exactly that length, in which case the array will end up not containing a string (ie it will contain characters that are not null-terminated).
I don't know if I understand correctly, but if I do, I am posting an example where you can pass an array of "strings" (which in C is represented as an array of arrays of char). Then you can compare the two first strings in your array
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* my_function(char *strings[]) {
char *ptrToString = NULL;
if (strcmp(strings[0],strings[1]) > 0) // Do you really mean '==1' here?
{
ptrToString = strings[1];
} else {
ptrToString = strings[0];
}
printf ("%s\n", ptrToString); // No need for '*', %s takes a pointer to char as argument
return ptrToString;
}
void main (void) {
char *a[] = {"dog", "cat"};
my_function(a);
}
Notes: * I changed "strcmp() == 1" to checking if the return is possitive or not. Checking for a specific value is unconventional (might not match your C implementation). In the documentation, the only guarantee is that strcmp will return positive, negative or zero, but not a specific value. http://linux.die.net/man/3/strcmp * There must be at least two null-treminated strings in the array for my_function function to work without segfaulting.
I hope this guides you in the right direction.
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