用C語言的leetcode刷題之旅——儲存注意事項（保持更新）

最近博主看網上有人說一定要把leetcode前幾百道刷一遍，於是決定刷刷消遣一下，沒想到第一道題就出了問題，感覺想對算法和跑通算法之間還是隔了很遠，於是將所有刷題時遇到的問題彙總到這裏。

⚠️此篇文章是以問題爲單位寫的，所以完整代碼我不會貼在這裏，我在leetcode的用戶名和CSDN用戶名是一樣的，那裏我按題爲單位寫了題解，讀者可以去那裏看完整代碼。

一、不要忽視題目給定的任何參數

報錯信息

=================================================================
==29==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000038 at pc 0x000000405105 bp 0x7ffda29df000 sp 0x7ffda29deff8
READ of size 4 at 0x602000000038 thread T0
    #2 0x7f660e1e82e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
0x602000000038 is located 0 bytes to the right of 8-byte region [0x602000000030,0x602000000038)
allocated by thread T0 here:
    #0 0x7f660fa972b0 in malloc (/usr/local/lib64/libasan.so.5+0xe82b0)
    #3 0x7f660e1e82e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
Shadow bytes around the buggy address:
  0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa 00 00 fa fa 00[fa]fa fa fd fa fa fa fd fa
  0x0c047fff8010: fa fa fd fa fa fa 00 fa fa fa fa fa fa fa fa fa
  0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==29==ABORTING

題目、原因和解決方法

【leetcode第一題】要求從給定數組中找出相加爲給定數字的兩個數，用一個長度爲2的數組存放這兩個數的數組下標。題目給定的模板爲：
int* twoSum(int* nums, int numsSize, int target, int* returnSize){，其中returnSize是爲了讓你指定存放結果的數組的長度，雖然題目沒有告之這一點，但要記得加一句：

*returnSize = 2;

不然會報溢出的錯誤。

經驗小結

不要忽略題目給的參數，要認真思考每個參數的意義。

二、將結點鏈接到鏈表末尾

題目簡述和錯誤信息

【leetcode第二題】用兩個單鏈表分別逆序存儲兩個整數，一個結點中放一位。計算結果也逆序放在單鏈表中。

出現的錯誤是：輸出的結果是一個空的單鏈表。

錯誤原因和解決方法

改正之後的代碼中有很多處都出現了這兩行：

cur->next = (struct ListNode*)malloc(sizeof(struct ListNode));
cur=cur->next;

改正之前，這兩行寫反了…

可以想想寫反了會怎麼樣：cur先指向cur->next指向的位置（爲NULL），這個操作僅僅將cur賦值爲NULL，起不到讓結點的前驅指向它自己的作用。