使用指針算法的最大值2d數組

下面是使用指針算法的完整程序。此程序將根據需要替換2D數組-1中每列中的所有最大值。

#include <iostream>

int main()
{
    double array2d[5][5];
    double *ptr;
    ptr = array2d[0];
    //        initializing matrix
    for (int i = 0; i < 5; ++i) {
        for (int j = 0; j < 5; ++j) {
            if (j % 2 != 0) {
                array2d[i][j] = (i + 1) - 2.5;
            } else {
                array2d[i][j] = 2 * (i + 1) + 0.5;
            }
        }
    }

    //these(from this point on) are the things that i have added.
    //Everything above this comment is the same as your code.  

    double (*rowBegin)[5]  = std::begin(array2d);
    double (*rowEnd)[5] = std::end(array2d);

    while(rowBegin != rowEnd)
    {
        double *colBegin = std::begin(rowBegin[0]);
        double *colEnd = std::end(rowBegin[0]);
        
        double lowestvalue = *colBegin;//for comparing elements
        double *pointerToMaxValue = colBegin;
        
        while(colBegin!= colEnd)
        {
            if(*colBegin > lowestvalue)
            {
                lowestvalue = *colBegin;
                pointerToMaxValue = colBegin ;
            }
            colBegin = colBegin + 1;
        }
        double *newcolBegin = std::begin(rowBegin[0]);
        double *newcolEnd = std::end(rowBegin[0]);

        while(newcolBegin!=newcolEnd)
        {
            if(*newcolBegin == lowestvalue)
            {
                *newcolBegin = -1;  
            }
            ++newcolBegin;
        }
        ++rowBegin;
    }
    return 0;
}

程序可以在這里檢查。

您可以添加打印輸出數組的所有元素，以檢查上述程序是否將每列中的所有最大值替換為-1。