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Multi dimensional array of structs...

Posted on 2009-12-16
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Last Modified: 2012-05-08
I have a struct :

struct Person {
   int empNo;
   unsigned char fname;
   unsigned char lname;
}

I can declare this :

struct Person *personList;
personList = (struct Person *) malloc( 10 * sizeof(struct Person)));

and then do something like this:
personList[0].empNo = 12;

and so on.

How do I declare/initialize this struct so I can get 100 persons? in other words personList[10][10] ?
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Question by:Maarvaadi
2 Comments
 
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phoffric earned 2000 total points
ID: 26068340
Note: Your malloc has an imbalance of ().

I'll take you literally and just have a single char for fname and lname. (If you want a string, then use a char* or a char [].)

Well, you are saying slightly different things:
1. Explicit Multidimensional array:

struct Person personList[10][10] =
{
 { {101, 'f', 'l'},{102,'a','b'},{},...,{110, 'x', 'y'} }, // first 10 records
 { {111, 'w', 's'},{112,'a','b'},{},...,{} }, // 2nd 10
 {},
...
 {},
};

2. Using malloc's as in your example.
See code below:
#include <stdio.h>
#include <stdlib.h>

struct Person {
   int empNo;
   unsigned char fname;
   unsigned char lname;
};

void main() {
	struct Person *personList[10]; // define an array of 10 pointers to Person
	int i,j;
	char ln = 'a', fn='a';
	// malloc 10 records per pointer
	for( i=0; i<10; i++ ) {
		fn = 'a';
		personList[i] = (struct Person *) malloc( 10 * sizeof(struct Person));

		for( j=0; j<10; j++ )
		{	struct Person tmp = {10*i+j, fn, ln};
			personList[i][j] = tmp; // substitute 'a' and 'b' with proper values
			fn++;
		}
		ln++;
	}

	for( i=0; i<10; i++ ) {
		for( j=0; j<10; j++ ) {
			struct Person tmp = personList[i][j];
			printf("%3d  %c  %c\n", tmp.empNo, tmp.fname, tmp.lname);
		}
	}
	printf("\n");
}

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by:Maarvaadi
ID: 31667102
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