如何为表格，二维数组或多维数组的所有元素设置或初始化默认值 [英] how to set or initialize default value for all elements of a table or 2d array or multdimentional array

问题描述

我想为表或2d数组的所有元素设置默认的非零值. array [size] = {12}设置第一个元素仅12个，其他元素都连续为0.但是fill(array，array + size，12)只能将所有元素连续设置为12个. 2d数组.是否有任何方法可以使用fill()进行操作，或者没有使用double for循环直接初始化的任何方法

I want to set a default nonzero value for all elements of a table or 2d array. array[size]={12} sets first elements only 12 and others are all 0 in a row.But fill(array,array+size,12) sets all elements to 12 in a row only.I could't apply this for 2d array.Is there any way to do this using fill() or any way without direct initialization using double for loop

#include <iostream>
#include<algorithm>
#include<vector>
#include<stdlib.h>
using namespace std;

int main()
{
   int arra[10][10];//declare 2d array

  for(int k=0;k<10;k++)//takes k's value 10 for 10 rows
     fill(arra,arra+10,45);//select a row and set all columns to 45 didn't work

}

数组初始化 http://www.fredosaurus.com/notes-cpp/arrayptr/array -initialization.html

推荐答案

与使用一维数组的方法几乎相同:

Almost the same way as you would with a 1-dimensional array:

#include <iostream>
#include <iomanip>

int main() {
    int arr[10][10] = {
        {  1,  2,  3,  4,  5,  6,  7,  8,  9, 10 },
        {  2,  4,  6,  8, 10, 12, 14, 16, 18, 20 },
        {  3,  6,  9, 12, 15, 18, 21, 24, 27, 30 },
        {  4,  8, 12, 16, 20, 24, 28, 32, 36, 40 },
        {  5, 10, 15, 20, 25, 30, 35, 40, 45, 50 },
        {  6, 12, 18, 24, 30, 36, 42, 48, 54, 60 },
        {  7, 14, 21, 28, 35, 42, 49, 56, 63, 70 },
        {  8, 16, 24, 32, 40, 48, 56, 64, 72, 80 },
        {  9, 18, 27, 36, 45, 54, 63, 72, 81, 90 },
        { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 }
    };

    for(int i=0; i<10; ++i) {
        for(int j=0; j<10; ++j) {
            std::cout << std::setw(4) << arr[i][j];
        }
        std::cout << '\n';
    }
}

注意:第一个索引不需要值.在这种情况下，编译器将自动计算该索引.

NOTE: The first index does not require a value. In that case the compiler will automatically calculate this index.

int arr[][10] = { ... };

编辑

一种避免双循环的替代方法是:

An alternative that will avoid a double loop is:

## Heading ###include <iostream>
#include <iomanip>


int main() {
    int arr[10][10] = {}; // Initializes all values to 0
    for(int i=0; i<10; ++i ) arr[i][0] = 12;

    for(int i=0; i<10; ++i) {
        for(int j=0; j<10; ++j) {
            std::cout << std::setw(4) << arr[i][j];
        }
        std::cout << '\n';
    }
}

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