Tag: for-loop

c语言 – ++ i和i ++有什么区别?

在C中,使用++i和之间有什么区别i++,哪些应该在for循环的增量块中使用? ++i将增加值的值i,然后返回递增的值。 i = 1; j = ++i; (i is 2, j is 2) i++将递增值的值i,但返回在i递增之前保持的原始值。 i = 1; j = i++; (i is 2, j is 1) 对于一个for循环,要么工作。++i似乎更常见,也许是因为这是K&R中使用的。 在任何情况下,遵循准则“宁可++i过i++”,你会不会出问题。 有一对夫妇的关于效率的意见++i和i++。在任何非学生项目编译器中,都没有性能差异。您可以通过查看生成的代码来验证这一点,这些代码是相同的。 效率问题很有意思……这是我尝试回答的问题: C ++中的i ++和++ i之间是否存在性能差异? 正如On Freund所说,对于C ++对象来说,它是不同的,因为它operator++()是一个函数,编译器无法知道如何优化临时对象的创建以保存中间值。 i ++被称为Post Increment,而++ i被称为Pre Increment。 i++ i++是后增量,因为它i在操作结束后将值增加1。 让我们看看以下示例: int i = 1, j; j = i++; 这里的价值j =

Which is more performant for/forEach if we are accessing current item in loop?

问题内容: Every where people are saying for is more performant then forEach e.g. https://jsperf.com/for-vs-foreach/37 Javascript efficiency: ‘for’ vs ‘forEach’ But does it holds true when accessing current element in loop. If not why not if yes what about following code, which gives contradictory results in different cases: Logic: //---------------------------------------- var arr = , len =

Replace loop for apply or sappy?

问题内容: I have a program, but I need to replace loop for apply or sapply? Is this possible in my case? Can you help me? My code TD = stri_read_lines("script.R") chars = data.frame() for(i in 1:length(TD)){ if(TD[i] !='') { char= unlist(strsplit(TD[i], split="")) for ( j in 1:nchar(TD[i]) ) { chars =rbind(chars , data.frame(a=char[j], b=i, c=

Adding data to arrays Java

问题内容: I had an idea for a way to bypass the hard limit on spaces for a normal array in Java. Would this work? public class Array{ private int group; public void addNums(int nums) { int list = new int[group.length + nums.length]; for (int a = 0; a < group.length; a++) list[a] = group[a]; for