C++數(shù)據(jù)結(jié)構(gòu)之鏈表的創(chuàng)建
前言
1.鏈表在C/C++里使用非常頻繁, 因?yàn)樗浅J褂? 可作為天然的可變數(shù)組. push到末尾時(shí)對(duì)前面的鏈表項(xiàng)不影響. 反觀C數(shù)組和std::vector, 一個(gè)是靜態(tài)大小, 一個(gè)是增加多了會(huì)對(duì)之前的元素進(jìn)行復(fù)制改寫(xiě)(線程非常不安全).
2.通常創(chuàng)建鏈表都是有next這樣的成員變量指向下一個(gè)項(xiàng), 通過(guò)定義一個(gè)head,last來(lái)進(jìn)行鏈表創(chuàng)建. 參考函數(shù) TestLinkCreateStupid().
說(shuō)明
1.其實(shí)很早就知道另一種創(chuàng)建方式, 但是一直沒(méi)總結(jié). 沒(méi)見(jiàn)過(guò)的童鞋看看以下創(chuàng)建鏈表的方式你用了哪一種. linus說(shuō)了不會(huì)第一種的TestLinkCreateClever()根本不會(huì)用指針(看來(lái)我真不會(huì)用指針). 這種方式在循環(huán)里根本不用判斷, 可見(jiàn)效率有多高.
// test_shared.cpp : 定義控制臺(tái)應(yīng)用程序的入口點(diǎn)。//#include "stdafx.h"#include <memory>#include <string>#include <iostream>typedef struct stage_tag { int data_ready; /* Data present */ long data; /* Data to process */ struct stage_tag *next; /* Next stage */} stage_t;// 高效率的鏈表創(chuàng)建方式stage_t* TestLinkCreateClever(int stages){ stage_t *head = NULL,*new_stage = NULL,*tail = NULL; stage_t **link = &head; // 區(qū)別在這個(gè)指針地址變量上,它起到綁定新的stage的作用. for(int i =0; i<stages;++i) { new_stage = (stage_t*)malloc(sizeof(stage_t)); new_stage->data_ready = 0; new_stage->data = i; *link = new_stage; // 把新的stage賦值給link指向的指針地址 link = &new_stage->next; // 綁定下一個(gè)的指針地址 } tail = new_stage; *link = NULL; return head;}// 低效率的鏈表創(chuàng)建方式stage_t* TestLinkCreateStupid(int stages){ stage_t *head = NULL,*new_stage = NULL,*tail = NULL; for(int i =0; i<stages;++i) { new_stage = (stage_t*)malloc(sizeof(stage_t)); new_stage->data_ready = 0; new_stage->data = i; new_stage->next = NULL; if(tail) tail->next = new_stage; else head = new_stage; tail = new_stage; } return head;}int _tmain(int argc, _TCHAR* argv[]){ std::cout << "=== TestLinkCreateClever ===" << std::endl; auto first = TestLinkCreateClever(10); while(first) { std::cout << "data: " << first->data << std::endl; first = first->next; } std::cout << "=== TestLinkCreateStupid ===" << std::endl; auto second = TestLinkCreateStupid(10); while(second) { std::cout << "data: " << second->data << std::endl; second = second->next; } return 0;}
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