如何在C中定义数组

Question

I'm reading the book "Cracking the Coding Interview" which contains several examples of algorithms in C. I'd like to make programs which implement these algorithms and run them as I go along.

One such algorithm is "Min and Max 1" (from the "Big O" chapter):

int min = Integer.MAX_VALUE;
int max = Integer.MIN_VALUE;
for (int x : array) {
  if (x < min) min = x;
  if (x > max) max = x;
}

I've attempted to 'write a program around this' as follows:

#include<stdio.h>

int array[5] = [1, 3, 2, 5, 4];

int min = Integer.MAX_VALUE;
int max = Integer.MIN_VALUE;

int main(void):
{
  for (int x : array) {
    if (x < min) min = x;
    if (x > max) max = x;
  }
  printf("The minimum is %i", min)
  printf("The maximum is %i", max)
}

However, if I try to compile and run this I get the error: expected identifier before numeric constant int array[5] = [1, 3, 2, 5, 4]; . How would I correctly implement this algorithm for this example input array?

Answer 1

What you mean is the following

#include <stdio.h>
#include <limits.h>

#define N   5

int main( void ) 
{
    int array[N] = { 1, 3, 2, 5, 4 };

    int min = INT_MAX;
    int max = INT_MIN;

    for ( size_t i = 0; i < N; i++ )
    {
        if ( array[i] < min ) min = array[i];
        if ( max < array[i] ) max = array[i];
    }

    printf( "The minimum is %i\n", min );
    printf( "The maximum is %i\n", max );

    return 0;
}

The program output is

The minimum is 1
The maximum is 5

As for your program then it contains invalid constructions according to the C grammar.

In C++ the loop can look the same way as you showed.

#include <iostream>
#include <limits>

int main() 
{
    const size_t N = 5;
    int array[N] = { 1, 3, 2, 5, 4 };

    int min = std::numeric_limits<int>::max();
    int max = std::numeric_limits<int>::min();

    for ( int x : array )
    {
        if ( x < min ) min = x;
        if ( max < x ) max = x;
    }

    std::cout << "The minimum is " << min << std::endl;
    std::cout << "The maximum is " << max << std::endl; 

    return 0;
}

Take into account that there is no sense to declare the array like global.

As for the array definition in C then you can define it either like

int array[5] = { 1, 3, 2, 5, 4 };

(or using some named constant instead of the number 5)

or like

int array[] = { 1, 3, 2, 5, 4 };

In the last case the number of elements is equal to the number of the initializers. Or even you can use the following initialization

int array[] = { [0] = 1, [1] = 3, [2] = 2, [3] = 5, [4] = 4 };

Answer 2

A few issues:

1. int array[5] = [1, 3, 2, 5, 4]; needs to be int array[] = {1, 3, 2, 5, 4};

2. The short form for loop doesn't exist in C. (Are you using a C++11 compiler to compile C code? If so then saving your source file with a .c extension might be a simple way of putting it into C mode.) Use for (size_t i = 0; etc. instead and access the array elements by the index i .

3. Using min and max as variable names is to be discouraged as they frequently appear as macro definitions.

Answer 3

Use C syntax to implement it in C.

• Use {} , not [] , to define the initial values of arrays.
• Use INT_MIN and INT_MAX from limits.h to use minimum and maximum values of int .
• Don't place a colon after int main(void) .
• for (int x : array) is not supported in C. Use one of the supported forms of loops.
• Semicolons are required after each statements.

Here is an implementation in C99:

#include<stdio.h>
#include<limits.h>

int array[5] = {1, 3, 2, 5, 4};

int min = INT_MAX;
int max = INT_MIN;

int main(void)
{
  for (size_t i = 0; i < sizeof(array) / sizeof(*array); i++) {
    int x = array[i];
    if (x < min) min = x;
    if (x > max) max = x;
  }
  printf("The minimum is %i", min);
  printf("The maximum is %i", max);
}

Answer 4

Array is initialized inside {} not []

Looks like you copied it from wrong place or you are a java Programmer.

#include<stdio.h>

int a[5] = {1, 3, 2, 5, 4};

int min = Integer.MAX_VALUE;
int max = Integer.MIN_VALUE;


int main(void):
{

  for (int x : array) {
    if (x < min) min = x;
    if (x > max) max = x;
  }
  printf("The minimum is %i", min)
  printf("The maximum is %i", max)
}

This will still give you error if you want i can fix it. I left it so that you can learn this by your own.