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[英]I'm having trouble with my function for finding the lowest value in a 5x5 two dimensional array
[英]I'm having trouble finding the segmentation fault?
我已經編寫了一個程序來對C ++中的數組執行mergesort。 該程序可以正常編譯,但是當我運行它時,它會顯示“分段錯誤(核心已轉儲)”並退出。 我一直在嘗試調試它,但無濟於事。 我確定我在某個地方濫用了指針(因此出現了段錯誤),但是無法將其放置在何處。 有人可以幫我嗎? 謝謝。
#include<iostream>
#include<queue>
#include<algorithm>
#include<math.h>
using namespace std;
void merge(int a[],int start, int middle, int end)
{
int i;
queue<int> buffer1;
queue<int> buffer2;
for(i = start; i<=middle; i++)
buffer1.push(a[i]);
for(i = middle+1; i<=end; i++)
buffer2.push(a[i]);
i = start;
while((!buffer1.empty()) || (!buffer2.empty()))
{
if(buffer1.front() < buffer2.front())
{
a[i] = buffer1.front();
buffer1.pop();
i++;
}
else
{
a[i] = buffer2.front();
buffer2.pop();
i++;
}
}
while(!buffer1.empty())
{
a[i] = buffer1.front();
buffer1.pop();
i++;
}
while(!buffer2.empty())
{
a[i] = buffer2.front();
buffer2.pop();
i++;
}
}
void mergeSort(int a[], int start, int end)
{
int middle;
if(start<end)
{
middle = (start+end)/2;
mergeSort(a,start,middle);
mergeSort(a,middle+1,end);
merge(a, start, middle, end);
}
}
int main()
{
int b[6] = {7,8,0,4,5,1},s = 0, e = 5;
mergeSort(b,s,e);
for(int i = 0; i<6; i++)
cout<<b[i]<<endl;
}
這是調試器輸出的內容-
execve("./q1", ["./q1"], [/* 63 vars */]) = 0
brk(0) = 0x1cde000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fee90911000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=116033, ...}) = 0
mmap(NULL, 116033, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fee908f4000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/usr/lib/x86_64-linux-gnu/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \240\10\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=1566568, ...}) = 0
mmap(NULL, 3675328, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fee9036e000
mprotect(0x7fee904e1000, 2093056, PROT_NONE) = 0
mmap(0x7fee906e0000, 49152, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x172000) = 0x7fee906e0000
mmap(0x7fee906ec000, 13504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fee906ec000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360*\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=92504, ...}) = 0
mmap(NULL, 2188352, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fee90157000
mprotect(0x7fee9016d000, 2093056, PROT_NONE) = 0
mmap(0x7fee9036c000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15000) = 0x7fee9036c000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\v\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1869392, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fee908f3000
mmap(NULL, 3972864, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fee8fd8d000
mprotect(0x7fee8ff4d000, 2097152, PROT_NONE) = 0
mmap(0x7fee9014d000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c0000) = 0x7fee9014d000
mmap(0x7fee90153000, 16128, PROT_READ|PROT_WRITE, `enter code here`MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fee90153000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240U\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=1084840, ...}) = 0
mmap(NULL, 3174760, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fee8fa85000
mprotect(0x7fee8fb8c000, 2093056, PROT_NONE) = 0
mmap(0x7fee8fd8b000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x106000) = 0x7fee8fd8b000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fee908f2000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fee908f0000
arch_prctl(ARCH_SET_FS, 0x7fee908f0740) = 0
mprotect(0x7fee9014d000, 16384, PROT_READ) = 0
mprotect(0x7fee8fd8b000, 4096, PROT_READ) = 0
mprotect(0x7fee9036c000, 4096, PROT_READ) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fee908ef000
mprotect(0x7fee906e0000, 40960, PROT_READ) = 0
mprotect(0x604000, 4096, PROT_READ) = 0
mprotect(0x7fee90913000, 4096, PROT_READ) = 0
munmap(0x7fee908f4000, 116033) = 0
brk(0) = 0x1cde000
brk(0x1d10000) = 0x1d10000
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0} ---
+++ killed by SIGSEGV (core dumped) +++
Segmentation fault (core dumped)
您的while
狀況似乎不對。 只要兩個容器之一不為空,您就在循環,然后在它們上調用front()
成員函數。 您可能應該一直循環直到它們都包含元素,即在第21行使用&&
代替||
。
所以這條線
while((!buffer1.empty()) || (!buffer2.empty())) // change to &&
我不確定這是否會破壞代碼的邏輯正確性,但這是段錯誤的原因(它來自第25行)
段錯誤發生在行上: if (buffer1.front() < buffer2.front())
queue
通常只是作為deque
或list
的包裝器實現的,您可以找到更具描述性的警告,以防在queue
的方法中調用front
,就像在queue
的方法中那樣:
如果您在Visual Studio中的“調試”下運行,則當遇到段錯誤時,它將彈出此對話框,您可以單擊“重試”以保留所有狀態進行調試:
您的問題是在這條線上:
while ((!buffer1.empty()) || (!buffer2.empty()))
這意味着while
如果任 -loop執行buffer1
或 buffer2
非空。 您需要將該條件更改為:
while (!empty(buffer1) && !empty(buffer2))
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