使用结构体，错误的Array选择排序在C：＆QUOT;需要左值...＆QUOT; [英] Selection Sort in C using an Array of Struct, error: "lvalue required..."

问题描述

试图排序结构的数组。结构是TextArt低于

定义

  typedef结构//结构保存ASCII艺术
{
    焦炭ARTISTNAME [8​​0]; //艺术家的名字
    炭asciiArt [20] [80]; //按行实际的ASCII艺术行
    INT评级; //艺术评级
} TextArt;
 

我不认为结构有什么关系这虽然。我得到的编译器错误

错误：左值试图分配一个结构到另一个需要作为分配的左操作数（如下图所示）

  TEMP = asciiArt + pos_min;
asciiArt + pos_min = asciiArt + I; //此处错误
asciiArt +我= *温度; //错误也在这里
 

呼吁功能

 选择排序（artPtr，artArrSize）;
 

和全选择排序功能。是否有什么我不理解有关分配使用=在C结构？我认为这是非此即彼我对TextArt阵传球在某种程度上是错误的。请赐教谢谢。

 无效选择排序（TextArt * asciiArt，INT大小）
{
    // pos_min是短期的分钟的位置
    INT pos_min;
    TextArt *温度;
    INT I = 0;
    INT J = 0;    对于（i = 0; I＆LT;大小-1;我++）
    {
        pos_min = I; //设置pos_min数组的当前索引        为（J = I + 1; J＆LT;大小; J ++）
        {
            如果（（STRNCMP（（asciiArt + I） - ＆GT; ARTISTNAME，（asciiArt + J） - ＆GT; ARTISTNAME））小于0）
            {
                pos_min = j的; // pos_min将跟踪该min是在索引的，当交换发生这是需要
            }
        }    //如果pos_min不再等于I比必须是已发现了一个较小的值，所以一个交换必须发生
            如果（pos_min！=ⅰ）
            {
                的printf（复制...... \\ n）;
                TEMP = asciiArt + pos_min;
                asciiArt + pos_min = asciiArt + I;
                asciiArt +我= *温度;
    }
}
 

解决方案

交换两个结构正确的方法是：

 如果（pos_min！= 1）
{
    的printf（复制...... \\ n）;
    常量TextArt TEMP = asciiArt [pos_min] //等价于：*（asciiArt + pos_min）
    asciiArt [pos_min] = asciiArt [I]
    asciiArt [I] =温度;
}
 

Trying to sort an array of Structs. Struct is TextArt defined below

typedef struct  //struct that holds ASCII art
{
    char artistName[80];    //name of artist
    char asciiArt[20][80];  //actual ascii art line by line
    int rating;             //rating of art
}TextArt;

I don't think the struct has anything to do with this though. I get the compiler error

error: lvalue required as left operand of assignment when trying to assign one struct to another(seen below)

temp = asciiArt+pos_min;
asciiArt+pos_min = asciiArt+i;  //error here
asciiArt+i = *temp;  //error also here

Call to function

selectionSort(artPtr, artArrSize);

and full selection sort function. Is there something I'm not understanding about assigning structs in C using =? I thought it was either this or my passing of the TextArt array was somehow wrong. Please enlighten me and thank you.

void selectionSort(TextArt *asciiArt, int size)
{
    //pos_min is short for position of min
    int pos_min;
    TextArt *temp;
    int i=0;
    int j=0;

    for (i=0; i < size-1; i++)
    {
        pos_min = i;//set pos_min to the current index of array

        for (j = i + 1; j < size; j++)
        {
            if ((strncmp((asciiArt+i)->artistName, (asciiArt+j)->artistName)) < 0)
            {
                pos_min = j; //pos_min will keep track of the index that min is in, this is needed when a swap happens
            }
        }

    //if pos_min no longer equals i than a smaller value must have been found, so a swap must occur
            if (pos_min != i)
            {
                printf("copying...\n");
                temp = asciiArt+pos_min;
                asciiArt+pos_min = asciiArt+i;
                asciiArt+i = *temp;
    }
}

解决方案

A correct way to swap the two structs would be:

if (pos_min != i)
{
    printf("copying...\n");
    const TextArt temp = asciiArt[pos_min]; //equivalent to: *(asciiArt + pos_min)
    asciiArt[pos_min] = asciiArt[i];
    asciiArt[i] = temp;
}

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