Question

我这里有一个代码，可以让用户将数字输入到 3*4 矩阵中，该函数将确定用户输入的最大元素的索引位置。

这是所需的输出：

Enter the array:

23.5   35   2     10
4.5    3    45    3.5
35     44   5.5   9.6

The location of the largest element is at (1, 2)

我的代码的问题在于它为最大数组打印了错误的坐标。如果我采用上面显示的示例输出，则该位置的打印输出将是 (2,3)。我尝试的是在函数的 for 循环中减去 i 和 j 的值，但这仅适用于特定输入，一旦我开始用完全不同的一组数字更改它，坐标索引将不准确再次。

#include <iostream>
#include <iomanip>

using namespace std;

void locateLargest(const double a[][4], int location[]);

const int ROW_SIZE = 3;
const int COLUMN_SIZE = 4;

int main(){

int location [2];

double matrix [ROW_SIZE][COLUMN_SIZE];

double input;

cout<<"Enter the array: "<< endl;

for (int i = 0; i < ROW_SIZE; i++){
    for(int j = 0; j < COLUMN_SIZE; j++){
        cin>>input;
        matrix[i][j] =  input;
    }
}

 for(int i = 0; i < ROW_SIZE; i++){
    for(int j = 0; j < COLUMN_SIZE; j++){
        cout<< setw(4)<<matrix[i][j]<< " ";
    }
     cout<< endl;
}
cout<<" "<< endl;

    locateLargest(matrix, location);
}

void locateLargest(const double a[][4], int location[]){

    int i, j;
    double max= a[0][0]; 
    
    location[0]= 0;

    for(i = 1; i < ROW_SIZE; ++i){
        for(j = 0; j < COLUMN_SIZE; j++){

    if(max < a[i][j])
        location[0] = i;
        location[1]= j;
        max= a[i][j];
        }
    }
    cout << "The location of the largest element is at ("<< (location[0]) << " , "<< (location[1]) <<" )"<< endl;

}

Answer 1

在这个 for 循环中

for(i = 1; i < ROW_SIZE; ++i){

您完全跳过了矩阵的第一行。

而且你忘记初始化数组位置的第二个元素。

location[0]= 0;

也在这个 if 语句中

 if(max < a[i][j])
        location[0] = i;
        location[1]= j;
        max= a[i][j];

你错过了大括号。必须有

 if(max < a[i][j])
 {
        location[0] = i;
        location[1]= j;
        max= a[i][j];
 }

在整个程序中，您都使用幻数 4 而不是常量 COLUMN_SIZE。

并且该函数不应输出任何消息。决定是否输出消息的是函数的调用者。

该函数可以如下所示，如下面的演示程序所示。

#include <iostream>
#include <utility>

const size_t ROW_SIZE = 3;
const size_t COL_SIZE = 4;

std::pair<size_t, size_t> locateLargest( const double a[][COL_SIZE], size_t m )
{
    std::pair<size_t, size_t> location( 0, 0 );
    
    for ( size_t i = 0; i < m; i++ )
    {
        for ( size_t j = i == 0; j < COL_SIZE; j++ )
        {
            if ( a[location.first][location.second] < a[i][j] )
            {
                location = { i, j };
            }
        }
    }
    
    return location;
}

int main() 
{
    double a[ROW_SIZE][COL_SIZE] =
    {
        { 23.5,   35,   2,     10   },
        {  4.5,    3,  45,      3.5 },
        { 35,     44,   5.5,    9.6 }
    };
    
    auto location = locateLargest( a, ROW_SIZE );
    
    std::cout << "The location of the largest element " 
              << a[location.first][location.second] << " is at ("
              << location.first << " , "<< location.second << " )" 
              << '\n';

    return 0;
}

程序输出为

The location of the largest element 45 is at (1 , 2 )

更通用的函数定义可以如下所示，如下面的演示程序所示。

#include <iostream>
#include <utility>

template <typename T, size_t M, size_t N>
std::pair<size_t, size_t> locateLargest( const T ( &a )[M][N] )
{
    std::pair<size_t, size_t> location( 0, 0 );
    
    for ( size_t i = 0; i < M; i++ )
    {
        for ( size_t j = i == 0; j < N; j++ )
        {
            if ( a[location.first][location.second] < a[i][j] )
            {
                location = { i, j };
            }
        }
    }
    
    return location;
}

int main() 
{
    const size_t ROW_SIZE = 3;
    const size_t COL_SIZE = 4;

    double a[ROW_SIZE][COL_SIZE] =
    {
        { 23.5,   35,   2,     10   },
        {  4.5,    3,  45,      3.5 },
        { 35,     44,   5.5,    9.6 }
    };
    
    auto location = locateLargest( a );
    
    std::cout << "The location of the largest element " 
              << a[location.first][location.second] << " is at ("
              << location.first << " , "<< location.second << " )" 
              << '\n';

    return 0;
}

程序输出和上图一样就是

The location of the largest element 45 is at (1 , 2 )

求矩阵中最大元素的索引

1 个答案: