手动排序在C编程语言中链表 [英] Manually sort a linked list in the C programming language

问题描述

如何在C中的函数按名称进行排序链表？

 结构REC {
    焦炭名[20];
    INT NR;
    结构体REC * NEXTREC;
};
typedef结构REC录制; / *代名词结构REC * /
typedef的拍摄* RecPtr; / *代名词指针* /无效SortLinkedList（RecPtr *特征码，INT p_size）; / * *原型/
诠释主（）{
    RecPtr startPtr = NULL;
    / *填充UPP链接列表...大小=在列表*节点NR /
    SortLinkedList（安培; startPtr，大小）;
}无效SortLinkedList（RecPtr *特征码，诠释p_size）{
    INT I，J;
    RecPtr tempPtr;
    RecPtr currentPtr;
    RecPtr nextPtr;
    currentPtr = *特征码;
    nextPtr = currentPtr-＆GT; NEXTREC;
    为（J = 0; J＆下; = p_size; J ++）{/ *循环为节点NR * /
        对于（I = 0; I＆下; = p_size -1;我++）{/ *循环一比NR节点更少* /
            如果（的strcmp（currentPtr-＆GT;名称，nextPtr-＆GT;名称）小于0）{/ *它小于... * /
                tempPtr = currentPtr; / * ...交换与温度* /
                currentPtr = nextPtr; / *但这种排序doesn'nt工作* /
                nextPtr = tempPtr;
            }
           currentPtr = nextPtr;
           currentPtr = currentPtr-＆GT; NEXTREC;
        }
    }
}
 

解决方案

这个问题似乎是，你只是操纵指针，而不是对象本身。当你解决一个链表，需要的话必须打破链接和重新制定的。

例如，在你的情况下，有三通并且它们具有如在括号中指定要修改

prevPtr-> NEXTREC（这需要改变为指向nextPtr代替currentPtr）
currentPtr-> NEXTREC（这需要更改为指向nextPtr->的NEXTREC代替nextPtr）
nextPtr-> NEXTREC（这需要改变为指向currentPtr）

您一定需要有一个prevPtr并跟踪它在你的计划。

  NEXTREC NEXTREC NEXTREC
 

prevPtr --------------> currentPtr -------------------------> nextPtr --------------------------->（nextPtr-> NEXTREC）

需要改变，以

  NEXTREC NEXTREC NEXTREC
 

prevPtr ----------- ------------> nextPtr ------------------ > currentPtr ------------------->（nextPtr-> NEXTREC）

How do you sort a linked list by name in a function in C?

struct rec{
    char name[20];
    int nr;
    struct rec *nextRec;
};
typedef struct rec Rec; /* synonym for struct rec */
typedef Rec *RecPtr; /* synonym for pointer */

void SortLinkedList(RecPtr *sPtr, int p_size);/* prototype */
int main() {
    RecPtr startPtr = NULL;
    /* filling upp the linked list... size = nr of nodes in list */
    SortLinkedList(&startPtr, size);
}

void SortLinkedList(RecPtr *sPtr, int p_size){
    int i, j;
    RecPtr tempPtr;
    RecPtr currentPtr;
    RecPtr nextPtr;
    currentPtr = *sPtr;
    nextPtr = currentPtr->nextRec;
    for( j = 0; j <= p_size; j++) { /* loop for nr of nodes */
        for(i = 0; i <= p_size -1 ; i++) { /* loop for one less than nr of nodes */
            if(strcmp(currentPtr->name, nextPtr->name) < 0) { /* it less than ...*/
                tempPtr = currentPtr;/* ...swap with temp */
                currentPtr = nextPtr; /* but this sorting doesn'nt work */
                nextPtr = tempPtr;
            }
           currentPtr = nextPtr;
           currentPtr = currentPtr->nextRec;
        }
    }
}

解决方案

The problem seems to be that you are just manipulating the pointers and not the objects themselves. When you sort a linked list, you necessary have to break links and re-make them.

For example, in your case there are three links and they have to be modified as specified in the brackets.

prevPtr->nextRec (This needs to be changed to point to nextPtr instead of currentPtr) currentPtr->nextRec (This needs to be changed to point to nextPtr->nextRec instead of nextPtr) nextPtr->nextRec (This needs to be changed to point to currentPtr)

You necessarily need to have a prevPtr and keep track of it in your program.

        nextRec                   nextRec           nextRec

prevPtr -------------->currentPtr ------------------------->nextPtr---------------------------> (nextPtr->nextRec)

Needs to be changed to

           nextRec           nextRec              nextRec

prevPtr ----------------------->nextPtr ------------------> currentPtr-------------------> (nextPtr->nextRec)

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