getchar

getchar（） getch（） 和 getche（） 的区别

由 ε祈祈猫儿з 提交于 2019-12-17 01:40:54
getchar() getch()和getche()的区别： （有时候遍程序的时候，都会因为没有清空缓存区而导致结果错误，而且错误不易发现） getchar有一个int型的返回值.当程序调用getchar时.程序就等着用户按键.用户输入的字符被存放在键盘缓冲区中.直到用户按回车为止(回车字符也放在缓冲区中).每次从缓存区中读取一个字符并回显，其余的在再次调用的时候在继续读取，直到读取了回车字符，才停止，等待用户输入。（如果有次你还没有输入完你的字符就输入回车，然后在输入字符，那么这中间就会有一个回车当成了字符，导致结果不正确。有时候，输入的字符多了，用完了自己要用的字符后，一定要记得清空缓存区 fllush(stdin);，否则在下次调用getchar的时候，它会直接使用原来缓存区里的字符，而不是你新输入的字符）。getchar有一个int型的返回值，所以呢，它返回的是第一个字符的ascll码，出错返回-1，这个的头文件是stdio.h。 getch是直接获取字符的,不等用户按回车,只要用户按一个键,getch就立刻返回,getch返回值是用户输入的ASCII码,出错返回-1.输入的字符不会回显，getch（）经常用在调试中，用getch（）让程序卡住，等你输入任意键后，才会继续运行。这个必须引入头文件conio.h getche（）的功能是输入后立即从控制台取字符，不以回车为结束

C : How to simulate an EOF?

由 元气小坏坏 提交于 2019-12-17 01:02:54
问题 I am currently reading K&R's book and typing in the examples from the first section, and there are a couple of examples such as this: while((c = getchar()) != EOF) { //do something } I am testing these examples on a Windows box and thus running the compiled exe files from the cmd prompt. To test the example above, how do I simulate an EOF ? That is, basically how can I make the loop stop when testing the example from the command prompt? 回答1: To enter an EOF, use: ^Z ( Ctrl Z ) in Windows ^D

CF920F SUM and REPLACE 题解

由 白昼怎懂夜的黑 提交于 2019-12-16 10:14:04
CF920F SUM and REPLACE 线段树例题解析合集 和模板的不同之处在于修改时是改为每个数的约数个数，不难发现，当一个数x<=2时，x的约数个数与本身相等，修改多少次多不会在改变 先预处理出每个数的约数个数，用线段树维护区间最大值，若<=2，则直接结束递归 对于>2的数都要暴力修改，但由于每个数的约数个数下降很快，几次后便降到<=2，所以复杂度优秀(大约是nlogn？) 这题与 CF438D The Child and Sequence (区间取模)，类似，也可以维护区间最大值 CF920F： #include <bits/stdc++.h> using namespace std; #define rg register #define ll long long inline void read (int &x) { char ch = getchar(); x = 0; while (!isdigit(ch)) ch = getchar(); while (isdigit(ch)) x = x * 10 + ch - 48, ch = getchar(); } void print (ll x) { if (x > 9) print (x / 10); putchar (x % 10 + 48); } const int N = 3e5 + 10, M = 1e6

getchar() and scanf() skipped in C [duplicate]

由 人盡茶涼 提交于 2019-12-13 19:50:17
问题 This question already has an answer here : scanf Getting Skipped [duplicate] (1 answer) Closed 4 years ago . I'm currently writing a program that will copy or append one file's text into another. My problem comes up when the user is prompted whether they want to overwrite or append the file, scanf() and getchar() are both skipped. I have tried using numerous combinations of getchar()'s and scanf()'s along with fflush(stdin) and ensuring that all the files I had opened are close, but I still

Dealing with input in C

由 你离开我真会死。 提交于 2019-12-13 17:38:04
问题 A brief question really, looking for, wondering about, and asking for any tips for what the best way is to handle this type of input: word word word word word word word word word word word whereby the number of words on each line is totally random, and each separate word can be added to some data structure, like a linked list or tree for example. Fgets each line and parse? Getchar()? Any clues? 回答1: Reading one line at a time with fgets seems like the best option here. Then just use strtok or

Getting a single character without pressing enter [duplicate]

由 梦想的初衷 提交于 2019-12-13 14:22:13
问题 This question already has answers here : What is the equivalent to getch() & getche() in Linux? (6 answers) Closed 4 years ago . I'm trying to get a single character input from the user without the user having to press enter. I've tried this: #include <stdio.h> int main() { int input; for (;;) { input = getchar(); printf("%d\n", input); } } But not only does the user need to press enter, it also registers two presses (the input character and the newline character) ie: $ ./tests a 97 10 c 99

Why is type int needed to handle EOF and return of getchar()?

由 烂漫一生 提交于 2019-12-13 09:48:27
问题 As written in book- The problem is distinguishing the end of the input from valid data. The solution is that getchar returns a distinctive value when there is no more input, a value that cannot be confused with any real character. This value is called EOF,for "end of file." We must declare c to be a type big enough to hold any value that getchar returns. We can't use char since c must be big enough to hold EOF in addition to any possible char. Therefore we use int. main() { int c; c = getchar

getchar() not working in c

由 那年仲夏 提交于 2019-12-13 07:54:46
问题 getchar() is not working in the below program, can anyone help me to solve this out. I tried scanf() function in place of getchar() then also it is not working. I am not able to figure out the root cause of the issue, can anyone please help me. #include<stdio.h> int main() { int x, n=0, p=0,z=0,i=0; char ch; do { printf("\nEnter a number : "); scanf("%d",&x); if (x<0) n++; else if (x>0) p++; else z++; printf("\nAny more number want to enter : Y , N ? "); ch = getchar(); i++; }while(ch=='y'|

Why does getchar work like a buffer instead of working as expected in real-time

由 两盒软妹~` 提交于 2019-12-13 04:58:36
问题 This is my first question on stackoverflow. Pardon me if I haven't searched properly but I do not seem to find an explanation for this. Was just attempting an example from Bjourne Stroustroup's papers. Added my bits to see the array get re-sized as I type the text. But it doesn't seem to work that way! getchar() simply waits till I am done with entering all the characters and then it will execute the loop. As per the logic, it doesn't actually go into the loop, get a character, perform its

encode program using getchar from command line argument and putchar to send to decode

由 痞子三分冷 提交于 2019-12-12 18:21:58
问题 So I'm trying to make a encode/decode program. So far I'm stuck in the encode part. I have to be able to get a message from the command line arguments, and encode it using a seeded random number. This number will be given by the user as the first argument. My idea is to get the int from getchar and just add random number result to it. I then want to get it back to the std out so that another program can read it as an argument to decode it using the same seed. So far, I can't get the putchar
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