查找序列中的 2 个最大和最小整数

Question

我正在尝试在 class 中编写一个程序，它将找到给定序列中的 2 个最大和最小整数，然后将它们打印给用户。样本运行看起来像这样：

Enter the sequence size: 8
Enter the sequence: 5 8 9 12 -6 4 -8 10

The two smallest values are: -8 -6
The two largest values are: 12 10

不允许我使用排序或数组。我整晚都在做，但我似乎无法弄清楚，有人能指出我正确的方向吗？这是我目前停留的地方 - 它不会编译，因为 'small1' 和 'large1' 变量没有初始化，但是如果我将它们设置为零，它们在样本运行.

int small1, small2, large1, large2, loopcount, sequencevalue;
// Ask the user to enter the first number
cout << "Sequence Size: ";
cin >> loopcount;

// Enter the sequence and start the loop
cout << "\nEnter the Sequence: ";

for (int i = 0; i < loopcount; i++)
{
    cin >> sequencevalue;

    if (sequencevalue < small1)
    {
        small2 = small1;
        small1 = sequencevalue;
    }

    if (sequencevalue > large1)
    {
        large2 = large1;
        large1 = sequencevalue;
    }
}

// Small variables
if (small1 == 0)
{
    small1 = sequencevalue;
}
else
{
    if (sequencevalue < small1)
    {
        small2 = small1;
        small1 = sequencevalue;
    }
}

// Large variables
if (large1 == 0)
{
    large1 = sequencevalue;
}
else
{
    if (sequencevalue < large1)
    {
        large2 = large1;
        large1 = sequencevalue;
    }
}

// Final Output
cout << "Two smallest values: " << small1 << " " << small2 << "\n";
cout << "Two largest values: " << large2<< " " << large1 << "\n";

非常感谢您就此事提供的帮助，感谢您抽出宝贵时间。

Answer 1

您正在寻找 <climits>

注意这个程序的输出

#include <climits>
#include <iostream>

int main() {
    std::cout << INT_MAX << std::endl;
    std::cout << INT_MIN << std::endl;
    return 0;
}

Answer 2

您的程序有未定义的行为，因为您在 small1、small2、large1、large2 初始化之前使用它们。

初始化 small1 和 small2 的正确方法是：

int small1 = INT_MAX;
int small2 = INT_MAX;

初始化 large1 和 large2 的正确方法是：

int large1 = INT_MIN;
int large2 = INT_MIN;

更新

如果没有排序数组，正确更新数字的逻辑就不是直截了当的。下面包括一个可以正确计算 small1 和 small2 的工作程序。我会留给你扩展它来计算 large1 和 large2.

#include <iostream>
#include <sstream>
#include <climits>
#include <algorithm>

int main()
{
   std::istringstream str("8 5 8 9 12 -6 4 -8 10");

   int small1 = INT_MAX;
   int small2 = INT_MAX;

   int loopcount;
   bool small1_found = false;

   str >> loopcount;
   for (int i = 0; i < loopcount; ++i )
   {
      int sequencevalue;
      str >> sequencevalue;

      if ( sequencevalue < small1 )
      {
         int temp = small1;
         small1 = sequencevalue;
         if ( small1_found )
         {
            small2 = std::max(sequencevalue, temp);
         }
         small1_found = true;
      }

   }

   std::cout << "Two smallest values: " << small1 << " " << small2 << "\n";
}

输出：

Two smallest values: -8 -6

Answer 3

我包含了 climits 并更正了你的代码。

代码示例：

#include <iostream>
#include <climits>
using namespace std;

int main(){
    int count = 0;
    cout << "Sequence Size: ";
    cin >> count;

    int sequencevalue;

    int large1 = INT_MIN;
    int large2 = INT_MIN;
    int small1 = INT_MAX;
    int small2 = INT_MAX;

    for (int i = 0; i < count; i++){
        cin >> sequencevalue;
        if (sequencevalue >= large1) {
            large2 = large1;
            large1 = sequencevalue;
        }
        else if (sequencevalue > large2){
            large2 = sequencevalue;
        }
        if (sequencevalue <= small1) {
            small2 = small1;
            small1 = sequencevalue;
        }
        else if (sequencevalue < small2){
            small2 = sequencevalue;
        }
    }

    cout << "Sequence size is " << count << endl;
    if (0 == count) {}
    else if (1 == count){
        cout << "Smallest value: " << small1 << endl;
        cout << "Largest value: " << large1 << endl;
    }
    else{
        cout << "First and second smallest value: " << small1 << " " << small2 << endl;
        cout << "First and second largest value: " << large1 << " " << large2 << endl;
    }
    return 0;
}

上面的代码示例将相同的数字视为唯一元素（这可能导致第一个和第二个相同 smallest/largest）。

如果您需要忽略相同的数字作为唯一元素，则 for 循环应如下所示：

for (int i = 0; i < count; i++){
    cin >> sequencevalue;
    if (sequencevalue > large1) {
        large2 = large1;
        large1 = sequencevalue;
    }
    else if (sequencevalue != large1 && sequencevalue > large2){
        large2 = sequencevalue;
    }
    if (sequencevalue < small1) {
        small2 = small1;
        small1 = sequencevalue;
    }
    else if (sequencevalue != small1 && sequencevalue < small2){
        small2 = sequencevalue;
    }
}

Answer 4

int small1, small2, large1, large2, loopcount, sequencevalue;
// Ask the user to enter the first number
cout << "Sequence Size: ";
cin >> loopcount;

// Enter the sequence and start the loop
cout << "\nEnter the Sequence: ";

for (int i = 0; i < loopcount; i++)
{
cin >> sequencevalue;
if(i==0)
small1=sequencevalue;
small2=sequencevalue;
large2=sequencevalue;
large1=sequencevalue;}
if(i==1) 
{if(sequencevalue>small1)small2=sequencevalue;
else{
small2=small1;
small1=sequencevalue;
    }
large2=small1;
large1=small2;
}
if (sequencevalue < small1)
{
    small2 = small1;
    small1 = sequencevalue;
}

if (sequencevalue > large1)
{
    large2 = large1;
    large1 = sequencevalue;
}
}
// Final Output
cout << "Two smallest values: " << small1 << " " << small2 << "\n";
cout << "Two largest values: " << large2<< " " << large1 << "\n";

Answer 5

给你

#include <iostream>

int main() 
{
    while ( true )
    {
        // Ask the user to enter the first number
        std::cout << "Sequence Size: ";

        unsigned int loopcount;

        if ( not ( std::cin >> loopcount ) || ( loopcount == 0 ) ) break; 

        int small1, small2, large1, large2;

        // Enter the sequence and start the loop
        std::cout << "\nEnter the Sequence: ";

        unsigned int i = 0;

        for ( ; i < loopcount; i++ )
        {
            int sequencevalue;

            std::cin >> sequencevalue;

            if ( i == 0 )
            {
                small1 = sequencevalue;
                large1 = sequencevalue;
            }
            else
            {
                if ( large1 < sequencevalue )
                {
                    large2 = large1;
                    large1 = sequencevalue;
                }
                else if ( i == 1 || large2 < sequencevalue )
                {
                    large2 = sequencevalue;
                }

                if ( sequencevalue < small1 )
                {
                    small2 = small1;
                    small1 = sequencevalue;
                }
                else if ( i == 1 || sequencevalue < small2 )
                {
                    small2 = sequencevalue;
                }
            }
        }

        if ( i == 1 )
        {
            printf( "There is only one largest value %d\n",
                large1 );
            printf( "And only one mallest value %d\n",
                small1 );
        }
        else
        {
            printf( "The first largest value is %d and the second largest value is %d\n",
                large1, large2 );

            printf( "And the first smallest value is %d and the second smallest value is %d\n",
                small1, small2 );
        }

    }

    return 0;
}

程序输出看起来像

Sequence Size: 10
Enter the Sequence: 1 9 8 0 7 6 5 4 3 2
The first largest value is 9 and the second largest value is 8
And the first smallest value is 0 and the second smallest value is 1
Sequence Size: 0

查找序列中的 2 个最大和最小整数

Finding the 2 greatest and smallest integers in a sequence

c++

integer

for-loop

if-statement

sequence