mathematical knowledge
#include <iostream>
#include <string.h>
#include <algorithm>
using namespace std;
int main()
{
int t;
long long m,n;
cin>>n>>m;
cout<<(m-n%m)*(n/m)*(n/m-1)/2+(n%m)*(n/m+1)*(n/m)/2<<" "<<(n-m+1)*(n-m)/2<<endl;
return 0;
}
typedef struct node
{
int data;
struct node *next;
} LNode, *LinkList;
LinkList Unions(LinkList la, LinkList lb)
{
LNode *p, *q, *w, *u;
p = la->next;
q = lb->next;
w = la;
while (p && q)
{
if (p->data == q->data)
{
w->next = p;
w = w->next;
p = p->next;
u = q;
q = q->next;
free(u);
}
else if (p->data < q->data)
{
u = p;
p = p->next;
free(u);
}
else
{
u = q;
q = q->next;
free(q);
}
}
if (q)
{
p = q;
}
while (q)
{
u = q;
q = q->next;
free(u);
}
w->next = NULL;
free(lb);
return la;
}
rc = waitpid(-1, &status, WNOHANG);
Wait for any child process to exit so that it can be recovered. I suspect that calling WaitPid again when the parent process has already collected its body will be an error. And that explains the probabilistic problem. So write the following code to verify it.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
void sig_handle(int sig)
{
waitpid(-1, NULL, 0);
printf("llm->%s(%d)\n", __FUNCTION__, __LINE__);
}
int main(int argc, char *argv[])
{
int rtn = 0;
int pid = 0;
char *arg[] = {"date", NULL};
signal(SIGCHLD, sig_handle);
//signal(SIGCHLD, SIG_IGN);
while(1)
{
pid = fork();
if(!pid)
{
execvp("date", arg);
exit(1);
}
usleep(10*1000);
rtn = waitpid(pid, NULL, 0);
if(rtn < 0)
perror("waitpid");
//usleep(10*1000);
}
return 0;
}
If you add sleep before waitpid, the problem will be 100% duplicated. If you remove sleep, there will be no problem.
The solution
Given the current code logic, there is a problem with either Waitpid being removed, so the best course of action is to determine whether it is true or false. If Waitpid returns ECHILD, then ignore the error.
The system calls
This is not a problem with the system call. This is not a problem with the implementation of waitpid after fork. The implementation handles the signal accordingly. The SIGCHLD signal processing action is restored before fork, as follows:
int __libc_system(char *command)
{
int wait_val, pid;
__sighandler_t save_quit, save_int, save_chld;
if (command == 0)
return 1;
save_quit = signal(SIGQUIT, SIG_IGN);
save_int = signal(SIGINT, SIG_IGN);
save_chld = signal(SIGCHLD, SIG_DFL);
if ((pid = vfork()) < 0) {
signal(SIGQUIT, save_quit);
signal(SIGINT, save_int);
signal(SIGCHLD, save_chld);
return -1;
}
if (pid == 0) {
signal(SIGQUIT, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGCHLD, SIG_DFL);
execl("/bin/sh", "sh", "-c", command, (char *) 0);
_exit(127);
}
/* Signals are not absolutly guarenteed with vfork */
signal(SIGQUIT, SIG_IGN);
signal(SIGINT, SIG_IGN);
#if 0
printf("Waiting for child %d\n", pid);
#endif
if (wait4(pid, &wait_val, 0, 0) == -1)
wait_val = -1;
signal(SIGQUIT, save_quit);
signal(SIGINT, save_int);
signal(SIGCHLD, save_chld);
return wait_val;
}
weak_alias(__libc_system, system)
But finally found that the reason for this problem is!! In the case of Visual Studio default installation, there are files that are not checked by default, that is, they are not installed by default. (Also should be because Win10SDK installation failed, but how to install also can not install, even if…
, causing problems)
But!!!!! H and stdio.h exist in these files.
It is not installed by default, as shown in the figure below:
Because oneself is this pit for a long time, think the net search is all sorts of separate download, the latter search, and then reconfigure and so on incomparable trouble operation. Here are some of the easiest ways to do it once and for all
Solution:
Just go to Programs and Functions, go to VS, right-click, modify, and check those, and you’re done.
Right-click and go to Change
Then you can see:
Then, click More and Select – Modify (check the box). After the completion of the picture, found that I forgot that several are unsolved problems ticked)
C++, check, and then confirm the modification OK, wait for the installation, problem solved. You don’t have to go to download WindowsSDK yourself.
Solve!
(after this can be used, my development needs can basically meet, but this is the installation of Win10SDK failure, the helpless move)
Separate installation, you can reference this article: http://blog.csdn.net/hhh1108/article/details/50352027
There is also a point of benefit, so you can install to other disks. Configure it yourself. VS will be installed on the C drive.
Of course, if you can install the Win10SDK on your computer, you should not have this problem.
In the process of learning C with Visual Studio, we sometimes finished typing the code and found that the program could execute as well. But is it ever frustrating to press the enter key to execute the next command in the program and see the window flash back?Don’t worry. Just type the following simple code.
Just add the last line:
system(” pause “);
, don’t forget “; “Oh.
# include< stdio.h>
#include< stdlib.h>
main()
y>oplaceholder0;
*************;
*************;
system (” pause “); // Don’t forget the semicolon
}
Welcome to the land of the Kings 
Usage: put return (); Before the return statement, otherwise there is no meaning
Advantages: low overhead, receive a character to end the program
Cons: Use it on a case-by-case basis, because getchar (); You need to accept a string to represent the end, and some functions explicitly need to accept a string as the return value, if you use getchar (); To solve the flashback problem, which can be confusing and introduce errors when the program is running.
can see, although can solve the running results of the flashback problem, but in the processing is completely different, although in the operation is also approximately the same, but in the memory, CPU and other levels, overhead is sometimes different, so you can choose according to your preferences for a way for you ！！！！！ System (” pause “) is recommended; This way, the introduction and processing of files is also more careful, if there is a heavy use of system functionality is, of course. windows.h> #include< stdlib.h> Of course, it is suitable for those who use a lot of library functions
#include <stdio.h>
#include <stdlib.h>
int main()
{
int ch = 0;
while ((ch = getchar()) != EOF)
{
if (ch >= 65 && ch <= 90)
{
ch = ch + 32;
putchar(ch);
}
else if (ch >= 97 && ch <= 122)
{
ch = ch - 32;
putchar(ch);
}
else if (ch >= '0' && ch <= '9')
{
;
}
else
{
putchar(ch);
}
}
system("pause");
return 0;
}
2. For example
Output a diamond
#include<stdio.h>
#include<stdlib.h>
int main()
{
int line = 0;
int i = 0;
scanf_s("%d", &line);
for (i = 0; i < line; i++)
{
int j = 0;
for (j = 0; j < line-1-i ; j++)
{
printf(" ");
}
for (j = 0; j < 2 * i + 1; j++)
{
printf("*");
}
printf("\n");
}
for (i = 0; i < line-1; i++)
{
int j = 0;
for (j = 0; j <=i; j++)
{
printf(" ");
}
for (j = 0; j < (line-1-i)*2 - 1; j++)
{
printf("*");
}
printf("\n");
}
system("pause");
return 0;
}
One, the phenomenon
br> 
Second, the reason why
No Algorithm was found for: 08001000h-0800FFFFH, which means that the program size has exceeded the space address of 08001000H. So it’s an error
3. Solutions
Except for the five cliches
1. Array size is too small, resulting in access to the memory should not be accessed
2. A division by zero error occurred
3. A large array is defined inside a function, causing the program stack to run out
4, The pointer is used incorrectly, resulting in access to the memory should not be accessed
5. It is also possible that the program threw an unreceived exception
The author also found that sometimes open array on OJ is too large (global variables, can run normally in the local) will cause runtime error, we need to pay attention to.
Error LNK1168 cannot open E: clanguage\Project3\Debug\ project3.exe to write
The problem
Intellij idea programming 1. Black thick lines or black cursor 2. A solution that cannot wrap a line by carriage return. (Practical Recommendation Method 2)
reason: it is usually caused by accidentally pressing insert. Some computers abbreviate insert, putting Del and Ins together, and Ins is the insert key.
Method 1. Click Intellij Idea on the upper left corner of the main interface, File> Settings> The diagram below * * * *
Put him on the Use block caret, and you can get back to your old self. ***
Method 2 (recommended) : Press and hold the Fn+ INSERT key to restore directly.
note: do not press Fn+insert if Use block caret is checked, otherwise the enter key will fail to wrap.
PS: restore the enter enter key newline function solution:
cancel Use block caret in the check box (default is no check, no change can be ignored), and then hold down Fn+insert key, so that the cursor and return will return to the original.