我坚持以下几个部分：
显示数组的第一个和最后一个元素
如何在此程序中的指定索引之前显示数组的元素？
问题描述：
编写一个程序，该程序生成25个随机整数的数组，每个整数从3到7（使用函数randint（）生成这些数字），并包括以下所有方面。
您的计划
在main中声明数组（不允许使用全局变量！），
使用你的randint（）函数将上面的数组初始化为随机值3到7
为此，您必须编写下面提供的原型的函数定义：
void showArray ( int a[ ], int size ); // shows the array in the format "int a [ ] = { 3, 7, 4, ... ,5, 6, 3, 4, 7 } "
void showReverse ( int a[ ], int size ); // shows the array in reverse using the format "int a [ ] = { 7, 4, 3, 6, 5, ... , 4, 7, 3 } "
int lowest ( int a[ ], int size ); // finds and returns the lowest value in the array (should be 7)
int highest ( int a[ ], int size ); // finds and returns the highest value in the array (should be 3)
int sumArray ( int a[ ], int size ); // calculates and returns the sum of all values in the array
float averageVal ( int a[ ], int size ); // calculates and returns the average of all values in the array
int count5 ( int a[ ], int size ); // returns how many times the number 5 appears in the array
int firstMinusLast ( int a[ ], int size ); // returns the difference between the First Array Element - Last Array Element
void showBeforeIndex( int a [ ], int size, int index); // shows all array values before a specified index
void done ( ); // a function that shows the message "I am now done with CSS1! :)
int randint(int min, int max); // a function that returns a random integer between min and max
这是我到目前为止的代码 - 我是如何做数组的，用于显示第一个和最后一个数组元素之间的区别以及确定在指定索引之前显示数组元素的方法（对于例如，指数3）？
#include <time.h>
#include <iostream>
#include <stdlib.h>
using namespace std;
void showArray ( int a[ ], int size ); // shows the array in the format "int a [ ] = { 3, 7, 4, ... ,5, 6, 3, 4, 7 } "
void showReverse ( int a[ ], int size );
int lowest ( int a[ ], int size );
int highest ( int a[ ], int size );
int sumArray ( int a[ ], int size );
float averageVal ( int a[ ], int size );
int count5 ( int a[ ], int size ); // returns how many times the number 5 appears in the array
int firstMinusLast ( int a[ ], int size ); // returns the difference between the First Array Element - Last Array Element
void showBeforeIndex( int a [ ], int size, int index); // shows all array values before a specified index
void done ();
int randint(int min, int max); // a function that returns a random integer between min and max
int main ()
{
srand((int)time(NULL));
int i = 0;
const int size = 25; // size variable for arrays
int randint[size], lowest, highest;
cout << "Making an array of 25 random integers from 3 to 7!\n";
cout << "\n";
cout << "Original array a [ ] = {";
for(i; i < size; i++)
{
randint[i] = 3 + rand () % 5; // random number between 3 to 7
}
showArray(randint, size); // pass the array and its SIZE to function
cout << "}\n";
// Reversed array
// One way to reverse an array is to swap the first and last value,
// then swap the second and second-to-last value,
// then swap the third and third-to-last value, and so on...
cout << "\n" << "Reversed array a [ ] = { ";
int j = size-1; // initialize j to the last index
i = 0; // set i to the beginning index (i.e. index 0)
while( i <= j) // keep loop until i and j cross over
{
std::swap(randint[i], randint[j]); // swap the values at i-th and j-th index
i++; // move i forwards
j--; // move j backwards
}
showReverse(randint, size);
cout << "}\n";
lowest=randint[0];
highest=randint[0];
for (i = 0; i < size; i++)
{
if(randint[i]<lowest)
lowest=randint[i];
if(randint[i]>highest)
highest=randint[i];
}
cout<<"\nLowest value is : "<<lowest <<"\n";
cout<<"\nHighest value is : "<<highest <<"\n";
int sum=0;
for (int a=0; a<size; a++)
{
sum+=randint[a];
}
cout << "\nThe sum of all array elements is " << sum << endl;
float average=sum/size;
cout << "\nThe average of all array values is " << average << endl;
int numsearch = 5;
int counter = 0;
for(int i = 0; i < size; i++)
if(randint[i] == numsearch)
counter++;
std::cout << "\nThe number 5 appears " << counter <<" times.\n";
std::cout << firstMinusLast;
return 0;
}
// Function definitions
void showArray ( int a[ ], int size )
{
for(int i = 0; i < size; i++) std::cout << a[i] << " ";
}
void showReverse ( int a[ ], int size )
{
for(int i = 0; i < size; i++) std::cout << a[i] << " ";
}
int count5(int numsearch, int randint[], int size)
{
int counter = 0;
for(int a = 0; a < size; a++)
if(randint[a] == numsearch)
counter++;
return counter;
}
int first (int size) /// find the first digit
{
while (size >=25)
size /= 25;
return size;
}
int last (int size) /// find the first digit
{
return (size%25);
}
int firstMinusLast ( int a[ ], int size )
{
int first = -1, last = -1;
for (int i=0; i<size; i++)
{
if (a != rand[i])
continue;
if (first == -1)
first = i;
last = i;
}
if (first != -1)
cout << "First minus last = " << first-last;
}
/* SAMPLE RUN:
ERRORS – will not compile; errors say:
||=== Build file: "no target" in "no project" (compiler: unknown) ===|
|In function 'int firstMinusLast(int*, int)'|
|214|warning: pointer to a function used in arithmetic [-Wpointer-arith]|
|214|error: comparison between distinct pointer types 'int*' and 'int (__attribute__((__cdecl__)) *)()' lacks a cast [-fpermissive]|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s))
*/
答案 0 :(得分：1)
你的问题非常混乱，包括不需要的代码片段。然而，我可以指出的一点是，你总结和平均数组元素的函数似乎已经以某种方式与main()合并。
请在main()中将它们分开并仅调用。 （注意，您可以使用求和函数来计算平均值）。
关于第一个问题，您可以计算数组的第一个和最后一个元素之间的差异，如下所示：
int firstMinusLast(int a[], int size)
{
return(a[0] - a[size-1]);
}
因为第一个元素总是带有索引零，所以无论如何都必须提供最后一个元素的索引。
要在指定的索引之前显示数组的元素，需要循环遍历它们，直到索引达到指定的值：
void ShowBeforeIndex(int a[], int size, int index)
{
for(int Ix = 0; Ix < index; Ix++)
cout << a[Ix] << " ";
}
请注意，只要您信任用户使用正确的索引调用函数，就不需要指定大小。