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嵌入式数据结构笔记（二）：内存工具与链表操作

news 2025/11/11 8:40:34

1.Valgrind 简介

Valgrind 是 GNU 提供的开源内存调试工具，主要用于检测以下问题：

内存错误（如非法访问、越界读写）
内存泄漏（已分配但未释放的内存）

2.Valgrind 安装

网络配置
确保系统网络连接正常，以下为典型安装流程图示。

解除系统锁

安装的时候报错，需要sudo命令来删除锁，删除完再安装。

sudo rm /var/lib/dpkg/lock-frontend  
sudo rm /var/lib/dpkg/lock

安装工具

sudo apt-get install valgrind

运行检测
通过以下命令检测程序内存问题：

valgrind ./a.out

2.链表核心操作

查找算法

中间节点：使用快慢指针法，快指针每次移动两步，慢指针每次移动一步。

倒数第k节点：双指针法，前指针先移动k步，后指针再同步移动。

//查找中间结点，不知道长度的情况下
Node_t *midnode(Link_t *plink)
{if(plink->phead == NULL){return NULL;}Node_t *ptmp = plink->phead;int len = 0, i;while(ptmp){ptmp = ptmp->pnext;++len;}ptmp = plink->phead;for(i = 1;i <= len / 2  ;++i){ptmp = ptmp->pnext;}return ptmp;
}//快慢指针法找中间结点（时间复杂度低）
Node_t *fsmidnode(Link_t *plink)
{if(plink->phead == NULL){return NULL;}Node_t *pfast = plink->phead;Node_t *pslow = plink->phead;while(NULL != pfast){pfast = pfast -> pnext;if(NULL == pfast){break;}pfast = pfast -> pnext;pslow = pslow -> pnext;}return pslow;
}

//查找倒数第k个结点，不知道长度的情况下
Node_t *k(Link_t *plink, int k)
{if(plink->phead == NULL){return NULL;}Node_t *ptmp = plink->phead;int len = 0, i;while(ptmp){ptmp = ptmp->pnext;++len;}ptmp = plink->phead;for(i = 1;i <= len - k;++i){ptmp = ptmp->pnext;}return ptmp;
}//快慢指针找倒数第k个
Node_t *knode(Link_t *plink, int k)
{if(plink->phead == NULL){return NULL;}Node_t *pfast = plink->phead;Node_t *pslow = plink->phead;int i;for(i = 1;i <= k;++i){if(NULL == pfast){return NULL;}pfast = pfast -> pnext;}while(NULL != pfast){pslow = pslow -> pnext;pfast = pfast -> pnext;}return pslow;
}

3.结构调整

链表逆序：通过迭代或递归反转指针方向。

void reverslink(Link_t *plink)
{if(plink->phead == NULL){return;}Node_t *pinsert = NULL;Node_t *ptmp = plink->phead;plink->phead = NULL;while (ptmp != NULL){pinsert = ptmp;ptmp = ptmp->pnext;pinsert->pnext = plink->phead;plink->phead = pinsert;}
}

链表排序

void insertSort(Link_t *plink)
{if(plink->phead == NULL){return;}Node_t *pinsert = plink -> phead -> pnext;Node_t *ptmp = plink -> phead -> pnext;Node_t *p = plink -> phead;plink -> phead -> pnext = NULL;while(ptmp){ptmp = ptmp -> pnext;if(plink -> phead -> data >= pinsert -> data){pinsert -> pnext = plink -> phead;plink ->phead = pinsert;}else{p = plink -> phead;while(p -> pnext != NULL && (pinsert -> data) > (p -> pnext -> data)){p = p -> pnext;}pinsert -> pnext = p -> pnext;p -> pnext = pinsert;}pinsert = ptmp;}
}

4.环链检测

有环链表判断：快慢指针相遇即存在环。

void ringlink(Link_t *plink)
{if(plink->phead == NULL || plink -> phead -> pnext == NULL){return;}Node_t *ptmp = plink -> phead;while(ptmp -> pnext != NULL){ptmp = ptmp -> pnext;}ptmp -> pnext = plink -> phead;
}int islinkring(Link_t *plink)
{if(plink->phead == NULL || plink -> phead -> pnext == NULL){return 0;}Node_t *pfast = plink -> phead;Node_t *pslow = pfast;while(1){pfast = pfast -> pnext -> pnext -> pnext;pslow = pslow -> pnext;if(pfast == pslow && pfast != NULL && pslow != NULL){break;}}return 1;
}

约瑟夫问题：通过循环链表模拟 Elimination Game。

Node_t *last_node(Link_t *plink, int clen)
{ringlink(plink);Node_t *ptmp = plink -> phead;Node_t *p = ptmp;Node_t *q;while(clen != 1){q = ptmp -> pnext;ptmp = ptmp -> pnext -> pnext;p = ptmp -> pnext;free(ptmp);ptmp = p;q -> pnext = ptmp;--clen; } return p;
}