multidimensional-array

问题 I am unable to find in the C standard docs specifically where it says that multidimensional arrays are contiguous. While it can be inferred from the fact that array elements are contiguous, I want some perspective from the community. The following code prints out the numbers in the order that I would expect, which is 1 - 9. #include <stdio.h> int main() { int a[][3] = {{1,2,3},{4,5,6},{7,8,9}}; int* p = (int*)a; int i; for (i = 0; i < sizeof(a)/sizeof(int); i++) printf("%d ",p[i]); return 0;

问题 I am a beginner trying to learn C++. Apologies if my question is not structured properly? I was working with arrays and found out that I can manipulate the values stored in an array through a function without using the & or pass by reference sign. I don't understand how this is possible as the lack of & sign means that it is passed by value and a copy is made which is manipulated. Elsewhere, I read that arrays are passed by pointers if this is the case I didn't use any explicit dereferencing

问题 I am a very new programmer, and have been struggling to write a method that can take any 2D array and fill it with random integers from 1 to 15. I believe I managed to build my method correctly, but I can't seem to see how to then call my method to fill the array I made in main. (I would have just filled it in main right out, but I'm trying to practice methods as well.) Here is the code I have so far. I appreciate any help you all are able to give me, thanks! using System; using System

问题 I was instructed not to use a storage array to complete this task. Basically, we have to create a function that rotates the contents of a 2d array 90 degrees. So if I start off with this array: int[][] array = {{1,2,3}, {4,5,6}, {7,8,9}}; The function should return an array like this: {{7,4,1}, {8,5,2}, {9,6,3}} Again we are not allowed to use a created array within the function for storage. Is it even possible to accomplish this without a storage array? 回答1: You can rotate/transpose the

问题 Consider the following code: int a[25][80]; a[0][1234] = 56; int* p = &a[0][0]; p[1234] = 56; Does the second line invoke undefined behavior? How about the fourth line? 回答1: It's up to interpretation. While the contiguity requirements of arrays don't leave much to the imagination in terms of how to layout a multidimensional arrays (this has been pointed out before), notice that when you're doing p[1234] you're indexing the 1234th element of the zeroth row of only 80 columns. Some interpret

问题 I have a matrix: R> pippo.m [,1] [,2] [,3] [,4] [1,] 1 2 3 4 [2,] 5 6 7 8 [3,] 9 10 11 12 [4,] 13 14 15 16 [5,] 17 18 19 20 [6,] 21 22 23 24 and I would like to transform this matrix in a 3D array with dim=(2,4,3). Passing through the transponse of pippo.m I am able to obtain a similar result but with columns and rows rotated. > pippo.t <- t(pippo.m) > pippo.vec <- as.vector(pippo.t) > pippo.arr <- array(pippo.vec,dim=c(4,2,3),dimnames=NULL) > pippo.arr , , 1 [,1] [,2] [1,] 1 5 [2,] 2 6 [3,]

问题 I need to merge those two arrays: $ar1 = array("color" => array("red", "green"), "aa"); $ar2 = array("color" => array( "green", "blue"), "bb"); $result = array_merge_recursive($ar1, $ar2); Expected output: [ 'color' => [ (int) 0 => 'red', (int) 1 => 'green', (int) 3 => 'blue' ], (int) 0 => 'aa', (int) 1 => 'bb' ] But it outputs: [ 'color' => [ (int) 0 => 'red', (int) 1 => 'green', (int) 2 => 'green', (!) (int) 3 => 'blue' ], (int) 0 => 'aa', (int) 1 => 'bb' ] I'm looking for the simplest way

问题 I know that the following is not correct: int arr[2][3] = {}; //some array initialization here int** ptr; ptr = arr; But I am quite surprised that the following lines actually work int arr[2][3] = {}; //some array initialization here auto ptr = arr; int another_arr[2][3] = {}; //some array initialization here ptr = another_arr; Can anyone possibly explain what is the type assigned to ptr in the second block of code, and what happened underneath? 回答1: Well, arrays decay to pointers when used

问题 I know that the following is not correct: int arr[2][3] = {}; //some array initialization here int** ptr; ptr = arr; But I am quite surprised that the following lines actually work int arr[2][3] = {}; //some array initialization here auto ptr = arr; int another_arr[2][3] = {}; //some array initialization here ptr = another_arr; Can anyone possibly explain what is the type assigned to ptr in the second block of code, and what happened underneath? 回答1: Well, arrays decay to pointers when used

问题 I am currently using xarray to make probability maps. I want to use a statistical assessment like a “counting” exercise. Meaning, for all data points in NEU count how many times both variables jointly exceed their threshold. That means 1th percentile of the precipitation data and 99th percentile of temperature data. Then the probability (P) of join occurrence is simply the number of joint exceedances divided by the number of data points in your dataset. <xarray.Dataset> Dimensions: (latitude: