srand

Strange behaviour of rand() in Xcode

由 懵懂的女人 提交于 2021-02-16 14:59:52
问题 While using Apple Xcode, the C program I include below will always return a 5 for y but z will return a random number, even though they have the same expression. Can you identify a reason for this behaviour? #include <stdio.h> #include <time.h> #include <stdlib.h> int main() { int x,y,z; srand((unsigned int)time(NULL)); x = ((unsigned int)time(NULL)); y=((double)rand()/(double)(RAND_MAX)*10); z=((double)rand()/(double)(RAND_MAX)*10); printf("Time %d\n", x); printf("\n"); printf("Number y %d\n

rand() gives almost the same number every time

由 不打扰是莪最后的温柔 提交于 2021-02-11 14:55:58
问题 I'm learning C and I want to generate a number between 0 and 6400. This is the code I came up with: #include <stdio.h> #include <stdlib.h> #include <time.h> int main() { srand(time(0)); int i = (rand() % 6401); printf("Random number between 0 and 6400: %d\n", i); return 0; } When I compile and run this code from the command line I get some very weird results: K:\C\Labo\Oefeningen 2019>a Random number between 0 and 6400: 6282 K:\C\Labo\Oefeningen 2019>a Random number between 0 and 6400: 6282 K

Why does my srand(time(NULL)) function generate the same number every time in c? [duplicate]

由 旧城冷巷雨未停 提交于 2020-08-19 17:46:44
问题 This question already has answers here : Random numbers in C (10 answers) How can I generate different random numbers for each player? (3 answers) Closed 2 years ago . So I was creating a program that would call a function and return 0 or 1 (0 meaning tails and 1 meaning heads) and then use that to print the outcome of 100 flips. It seemed simple enough thinking I could use srand(time(NULL)) to seed rand() with constantly varying seeds. Here was my first crack. #include <stdio.h> #include

Why does my srand(time(NULL)) function generate the same number every time in c? [duplicate]

由 南笙酒味 提交于 2020-08-19 17:46:42
问题 This question already has answers here : Random numbers in C (10 answers) How can I generate different random numbers for each player? (3 answers) Closed 2 years ago . So I was creating a program that would call a function and return 0 or 1 (0 meaning tails and 1 meaning heads) and then use that to print the outcome of 100 flips. It seemed simple enough thinking I could use srand(time(NULL)) to seed rand() with constantly varying seeds. Here was my first crack. #include <stdio.h> #include

Is it possible to increase the refresh speed of srand(time(NULL)) in C?

由 两盒软妹~` 提交于 2020-05-26 05:54:07
问题 I am asking to see if there is a way of increasing the speed the srand(time(NULL)); function "refreshes"? I understand srand() produces a new seed according to time (so once a second), but I am looking for an alternative to srand() that can refresh more often than 1 second intervals. When I run my program it produces the result it is supposed to, but the seed stays the same for essentially a second, so if the program is run multiple times a second the result stays the same. Sorry for such a

c语言寒假大作战03

由 扶醉桌前 提交于 2020-02-11 20:39:34
2.2.1作业头 问题 答案 这个作业属于那个课程 C语言程序设计 这个作业1要求在哪里 https://edu.cnblogs.com/campus/zswxy/CST2019-2/homework/10271 这个作业目标 使用函数、Switch语句来完成菜单程序 作业正文 https://www.cnblogs.com/galen123/p/12296356.html 其他参考文献 https://baijiahao.baidu.com/s?id=1616367741584583839&wfr=spider&for=pc 2.2.2 设计思路和遇到的问题 请写上你的心路历程和程序设计思路，并在其中写下你遇到的问题 1.srand((unsigned)time(NULL)），srand函数是随机数发生器的初始化函数。原型:void srand(unsigned seed); 2.字符型变量也for循坏的连接，以及printf语句的表达 3.rand函数的意思C 库函数 int rand(void) 返回一个范围在 0 到 RAND_MAX 之间的伪随机数。 4."function"：本地函数定义是非法的，代码尝试在函数内定义函数。或者，在 C2601 错误位置之前，你的源代码中可能有一个额外的大括号。 2.3 程序结果截图 2.2.4 程序代码 #include<stdio.h

C++随机数

由 和自甴很熟 提交于 2020-02-11 17:19:40
C++中的随机数（伪随机）产生不像其他语言直接通过Random函数生成，需要使用 cstdlib库中rand()函数。 产生 [a,n) 的随机数通用公式：a + rand() % n；其中的a是起始值，n是整数的范围。 一般为了产生不重复的随机数，会使用srand()函数设置种子，会以时间为种子。 srand((int)time(0));//产生随机数种子，srand()函数 例1 void Bank::Setaccount() { srand((int)time(0));//产生随机数种子，srand()函数 long tempcard = 0; for(int i = 0; i < 11; i++){ tempcard += tempcard*10 + rand() % 10;//要取得[0,n) 就是rand() %n 表示 从0到n-1的数 /*其他的随机数的范围通式 产生一定范围随机数的通用表示公式是： 要取得[0,n) 就是rand（）%n 表示 从0到n-1的数 要取得[a,b)的随机整数，使用(rand() % (b-a))+ a; 要取得[a,b]的随机整数，使用(rand() % (b-a+1))+ a; 要取得(a,b]的随机整数，使用(rand() % (b-a))+ a + 1; 通用公式:a + rand() % n；其中的a是起始值，n是整数的范围。

srand+rand() combination

由 ♀尐吖头ヾ 提交于 2020-01-30 15:53:28
#include <iostream> #include <cstdlib> /* include to allow rand() to be used */ #include<ctime>/*just used in function: time(NULL)*/ using namespace std; int main() { int x; /* variable to hold our random integer */ srand(time(NULL));//system's time, in seconds,if not, the value will not change x = rand(); cout << "x = " << x << endl; x = rand(); cout << "x = " << x << endl; return 0; } 来源： https://www.cnblogs.com/defoliate/p/12242879.html

Why does srand create same numbers?

由 回眸只為那壹抹淺笑 提交于 2020-01-24 21:14:41
问题 I wrote a program in c that creates randomly matrix. It creates a string like this (3,-6,2;5,2,-9;-8,20,7). ";" cuts every row and a "," every column. Now i wrote a rust program that makes matrixaddition or mult. I call it with this: ./matrix ./test 3 3 "*" ./test 3 3 ./matrix calls my rust program and i give it 3 arguments. (Matrix 1, Operator, Matrix2) It works and the calculation is fine but Matrix 1 and 2 are always equal. I think it is because I use srand depending on time and because i

Rand() % 14 only generates the values 6 or 13

由 折月煮酒 提交于 2020-01-18 04:44:42
问题 Whenever I run the following program the returned values are always 6 or 13. #include <iostream> #include <fstream> #include <ctime> #include <cstdlib> using namespace std; //void randomLegs(); //void randomPush(); //void randomPull(); //void randomMisc(); int main(int argc, const char * argv[]) { srand(time(NULL)); //randomLegs(); cout << rand() % 14; return 0; } I have run the program close to a hundred times during today and yesterday. Can anyone tell me what I'm doing wrong? Thank you.
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