c++ - 矩阵C++每一行中的最小元素

Question

这段代码只能返回矩阵中的一个最小元素，但是如果我想返回每一行中的最小元素怎么办？我需要在 C++ 中使用递归函数。谢谢你的帮助

#include<iostream>
using namespace std;
int smallest(int** arr, int rows, int columns, int column_index = 0)
{
    if (rows <= 0 || column_index >= columns)
        return INT_MAX;


    if (rows == 1)
        return min(*(*arr + column_index),       
            smallest(arr, 1, columns - 1,
                column_index + 1)); 


    return min(smallest(arr, 1, columns), 
        smallest(arr + 1, rows - 1, columns));
}
int main()
{
    int row, col, index=0;
    cin >> row;
    cin >> col;
    int** arr;
    arr = new int* [row];
    for (int i = 0; i < row; i++) {
         arr[i] = new int[col];
         for (int j = 0; j < col; j++) {
             cin >> arr[i][j];
           }
        }
    cout<<smallest(arr, row, col, index);
    return 0;
}

Answer 1

如果您使用标准算法，我认为这么多代码就足够了 - std::min_element :

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
    int r, c;
    std::cin >> r >> c;
    std::vector<std::vector<int>> mat(r, std::vector<int>(c));
    for (auto &&row : mat)
        for (auto &&ele : row)
            std::cin >> ele;
    for (auto &&row : mat)
        std::cout << *std::min_element(row.begin(), row.end()) << std::endl;
}

如果你想按照自己的方式做(老派风格，使用递归)，那么做这样的事情。您只需要在调用 smallest 时修复行的索引.下面是一些不言自明的代码:

#include <algorithm>
#include <iostream>

// here row_index represents the index of row and col represents the number of
// elements in that row which are not yet traversed (counted from beginning)
int smallest(int **arr, int row_index, int col) {

    // only first element is not traversed
    if (col == 1)
        return arr[row_index][0];

    // return minimum of last element and value returned by recursive call for
    // first col - 1 elements
    return std::min(arr[row_index][col - 1], smallest(arr, row_index, col - 1));
}

int main() {
    int row, col;
    std::cin >> row;
    std::cin >> col;
    int **arr = new int *[row];
    for (int i = 0; i < row; i++) {
        arr[i] = new int[col];
        for (int j = 0; j < col; j++)
            std::cin >> arr[i][j];
    }

    // call the function for each row
    for (int i = 0; i < row; i++)
        std::cout << "Smallest element in row " << i + 1 << " : "
                  << smallest(arr, i, col) << '\n';
}