顯示 4 個整數中的最大值和最小值，同時顯示它們的位置

Question

這是我在大學學習 Comp-Sci class 的第一年，在此 class 之前我沒有編程經驗。 I'm currently trying to write a C program for a class assignment which takes in 4 integer inputs and then displays the largest and smallest of the 4, while also stating the position in which the largest and smallest integers were inputted.

注意：我不允許使用任何函數、arrays 或循環（除了下面給出的 while 循環，但僅此而已）。

我的教授提供了一個大綱來幫助入門。

這是我的代碼：

#include <stdio.h>

int main(void)
{
    int x1, x2, x3, x4;
    int xlarge, xsmall, ixlarge, ixsmall;

    while (1)
    {
        printf("enter x1, x2, x3, x4:\n");
        scanf("%d%d%d%d", &x1, &x2, &x3, &x4);

        /*     add code to calculate xlarge, xsmall,
         *     ixlarge, ixsmall
         * --> between here */

        if ((x1 > x2) && (x1 > x3) && (x1 > x4))
            x1 = xlarge;
        else if ((x2 > x1) && (x2 > x3) && (x2 > x4))
            x2 = xlarge;
        else if ((x3 > x1) && (x3 > x2) && (x3 > x4))
            x3 = xlarge;
        else if ((x4 > x1) && (x4 > x2) && (x4 > x3))
            x4 = xlarge;

        if ((x1 < x2) && (x1 < x3) && (x1 < x4))
            x1 = xsmall;
        else if ((x2 < x1) && (x2 < x3) && (x2 < x4))
            x2 = xsmall;
        else if ((x3 < x1) && (x3 < x2) && (x3 < x4))
            x3 = xsmall;
        else if ((x4 < x1) && (x4 < x2) && (x4 < x3))
            x4 = xsmall;

        if (xlarge = x1)
            ixlarge = 1;
        else if (xlarge = x2)
            ixlarge = 2;
        else if (xlarge = x3)
            ixlarge = 3;
        else if (xlarge = x4)
            ixlarge = 4;

        if (xsmall = x1)
            ixsmall = 1;
        else if (xsmall = x2)
            ixsmall = 2;
        else if (xsmall = x3)
            ixsmall = 3;
        else if (xsmall = x4)
            ixsmall = 4;

        /* <-- and here */

        printf("largest = %4d at position %d, ", xlarge, ixlarge);
        printf("smallest = %4d at position %d\n", xsmall, ixsmall);
    }

    while (1) getchar();
    return 0;
}

據我了解，如果滿足條件，該程序應該將xlarge和xsmall分配給輸入，對於ixlarge和ixsmall也是如此。 但是，我在嘗試運行該程序時遇到的一個問題是xlarge和xsmall顯然未初始化，我不知道從哪里開始。

Answer 1

看代碼：

它應該是xlarge = x1而不是x1 = xlarge並且類似地xsmall = x1因為它是 xlarge 存儲 x1 的值，而不是相反。

你也可以像這樣使用你的 if-else：

if ((x1 > x2) && (x1 > x3) && (x1 > x4))
{
xlarge = x1;
ixlarge = 1;
}
else if ((x2 > x1) && (x2 > x3) && (x2 > x4))
{
xlarge = x2;
ixlarge = 2;
}

等等...

Answer 2

當你認為你的問題太難時

將您的問題分成小塊或簡化您的問題

1.獲取我輸入的內容（1 個整數）並顯示出來

2.獲取我輸入的內容（2個整數）並顯示出來

3.比較我的key in(2 integers) 越來越小並顯示出來

4.獲取我輸入的（3個整數）並顯示它，比較我輸入的（3個整數）更大和更小並顯示它

5.嘗試4個整數

這不是關於編程，而是關於我想告訴你的學習方法。

1.

#include <stdio.h>
#include <stdlib.h>



int main() {
    int FirstKeyIn;
    scanf("%d",&FirstKeyIn);
    printf("I key in :%d \n",FirstKeyIn);



    return 0;
}

2.

#include <stdio.h>
#include <stdlib.h>



int main() {
    int FirstKeyIn,SecondKeyIn;
    scanf("%d %d",&FirstKeyIn,&SecondKeyIn);
    printf("First  key in :%d \n",FirstKeyIn);
    printf("Second key in :%d \n",SecondKeyIn);


    return 0;
}

3.

#include <stdio.h>
#include <stdlib.h>



int main() {
    int FirstKeyIn,SecondKeyIn;
    int Bigger,Smaller;
    scanf("%d %d",&FirstKeyIn,&SecondKeyIn);
    printf("First  key in :%d \n",FirstKeyIn);
    printf("Second key in :%d \n",SecondKeyIn);
    if(FirstKeyIn>SecondKeyIn){
        Bigger=FirstKeyIn;//save FirstKeyIn value into Bigger
        Smaller=SecondKeyIn;//save SecondKeyIn value into Smaller
    }else{
        Bigger=SecondKeyIn;//save SecondKeyIn value into Bigger
        Smaller=FirstKeyIn;//save FirstKeyIn value into Smaller
    }
    printf("Bigger value is :%d \n",Bigger);
    printf("Smaller value is :%d \n",Smaller);
    return 0;
}

4.

#include <stdio.h>
#include <stdlib.h>



int main() {
    int FirstKeyIn,SecondKeyIn,ThirdKeyIn;
    int Bigger,Smaller;
    scanf("%d %d %d",&FirstKeyIn,&SecondKeyIn,&ThirdKeyIn);
    printf("First  key in :%d \n",FirstKeyIn);
    printf("Second key in :%d \n",SecondKeyIn);
    printf("Third key in :%d \n",ThirdKeyIn);
    if(FirstKeyIn>SecondKeyIn){
        Bigger=FirstKeyIn;//save FirstKeyIn value into Bigger
        Smaller=SecondKeyIn;//save SecondKeyIn value into Smaller
    }else{
        Bigger=SecondKeyIn;//save SecondKeyIn value into Bigger
        Smaller=FirstKeyIn;//save FirstKeyIn value into Smaller
    }

    if(ThirdKeyIn>Bigger){
        Bigger=ThirdKeyIn;//save ThirdKeyIn value into Bigger
    }
    if(ThirdKeyIn<Smaller){
        Smaller=ThirdKeyIn;//save ThirdKeyIn value into Smaller
    }


    printf("Bigger value is :%d \n",Bigger);
    printf("Smaller value is :%d \n",Smaller);
    return 0;
}

---

最大，最小位置

#include <stdio.h>
#include <stdlib.h>



int main() {
    int FirstKeyIn,SecondKeyIn,ThirdKeyIn;
    int Bigger,Smaller;
    int MaxPlace,MinPlace;
    scanf("%d %d %d",&FirstKeyIn,&SecondKeyIn,&ThirdKeyIn);
    printf("First  key in :%d \n",FirstKeyIn);
    printf("Second key in :%d \n",SecondKeyIn);
    printf("Third key in :%d \n",ThirdKeyIn);
    if(FirstKeyIn>SecondKeyIn){
        Bigger=FirstKeyIn;//save FirstKeyIn value into Bigger
        Smaller=SecondKeyIn;//save SecondKeyIn value into Smaller
        MaxPlace=1;
        MinPlace=2;
    }else{
        Bigger=SecondKeyIn;//save SecondKeyIn value into Bigger
        Smaller=FirstKeyIn;//save FirstKeyIn value into Smaller
        MaxPlace=2;
        MinPlace=1;
    }

    if(ThirdKeyIn>Bigger){
        Bigger=ThirdKeyIn;//save ThirdKeyIn value into Bigger
        MaxPlace=3;
    }
    if(ThirdKeyIn<Smaller){
        Smaller=ThirdKeyIn;//save ThirdKeyIn value into Smaller
        MinPlace=3;
    }


    printf("Bigger value is :%d \n",Bigger);
    printf("Bigger Place is :%d \n",MaxPlace);
    printf("Smaller value is :%d \n",Smaller);
    printf("Smaller Place is :%d \n",MinPlace);
    return 0;
}

5.

自己試試

Answer 3

您需要注意多點。

如果您需要多次運行您的程序，那么您需要一個哨兵控制循環（例如，由諸如是/否或特定重復次數等條件控制），而不是無限循環，即while(1) 。 如果不是，則不需要while循環。

在程序結束時， getchar()會一直阻塞，直到按下ENTER ，所以你不需要那個while(1) 。

您可以簡單地使用一個塊在if-else-if中編寫多個語句，這樣您就不必在最后再次檢查索引，例如：

if ((x1 > x2) && (x1 > x3) && (x1 > x4))
{ 
    xlarge = x1; // assign the number to xlarge, not x1 = xlarge
    ixlarge = 1; // assign the position of the number here!!!
}

您正在分配x1 = xlarge; 這是不正確的，因為x1已經包含用戶輸入的值。 該值將被存儲在xlarge中的垃圾值覆蓋，因為它尚未初始化。 它應該是： xlarge = x1; .

在if-else中，您不需要檢查最后一個條件，即已經測試了三個備選方案，因此您可以簡單地編寫最后一個結果，而無需在else中對其進行測試。

     if ( condition-1 ) /* do something */
else if ( condition-2 ) /* do something */
else if ( condition-3 ) /* do something */
else                    /* do something if all other conditions are false */

始終初始化您的變量，以便您確定它們位於已知的 state 中，並且不會導致used-before-initialization導致Undefined Behavior 。

這是一個例子（現場）：

#include <stdio.h>

int main(void)
{
    int x1 = 0, x2 = 0, x3 = 0, x4 = 0;
    int xlarge = 0, xsmall = 0, ixlarge = 0, ixsmall = 0;

    printf("Enter x1, x2, x3, x4: ");
    scanf("%d %d %d %d", &x1, &x2, &x3, &x4);

    if ((x1 > x2) && (x1 > x3) && (x1 > x4))
    { 
        xlarge = x1;
        ixlarge = 1;
    }
    else if ((x2 > x1) && (x2 > x3) && (x2 > x4))
    { 
        xlarge = x2;
        ixlarge = 2;
    }
    else if ((x3 > x1) && (x3 > x2) && (x3 > x4))
    { 
        xlarge = x3;
        ixlarge = 3;
    }
    else if ((x4 > x1) && (x4 > x2) && (x4 > x3))
    { 
        xlarge = x4;
        ixlarge = 4;
    }

    if ((x1 < x2) && (x1 < x3) && (x1 < x4))
    {
        xsmall = x1;
        ixsmall = 1;
    }
    else if ((x2 < x1) && (x2 < x3) && (x2 < x4))
    {
        xsmall = x2;
        ixsmall = 2;
    }
    else if ((x3 < x1) && (x3 < x2) && (x3 < x4))
    {
        xsmall = x3;
        ixsmall = 3;
    }
    else if ((x4 < x1) && (x4 < x2) && (x4 < x3))
    {
        xsmall = x4;
        ixsmall = 4;
    }

    printf("Largest  %d @ [index: %d]\n", xlarge, ixlarge);
    printf("Smallest %d @ [index: %d]\n", xsmall, ixsmall);

    return 0;
}

Output：

Enter x1, x2, x3, x4: 1 2 3 4
Largest  4 @ [index: 4]
Smallest 1 @ [index: 1]

---

如果您被允許使用宏，那么您可以為您的條件編寫：

#define IS_GREATER(n,x,y,z)     ((n > x) && (n > y) && (n > z))
#define IS_SMALLER(n,x,y,z)     ((n < x) && (n < y) && (n < z))

這是一個宏示例： http://ideone.com/G18hci

---

注意：請記住，您的解決方案不會處理重復元素用例或所有元素都相同的情況。