[LeetCode 解題筆記] Transpose Matrix

原問題網址：867. Transpose Matrix

問題描述

給定 2D 整數陣列 matrix ，return 它的轉置矩陣。

解題思路

這一題本身沒什麼難度，算是滿經典的題目。唯一要注意的是參數中的 int** returnColumnSizes 是「pointer to a pointer to an integer」。

/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
int** transpose(int** matrix, int matrixSize, int* matrixColSize, int* returnSize, int** returnColumnSizes){
  int row = matrixSize;
  int col = *matrixColSize;
  *returnSize = col;
  *returnColumnSizes = malloc(sizeof(int) * col); 
  for (int i = 0; i < col; i++) {
    (*returnColumnSizes)[i] = row;
  }
    
  int **transposedMatrix = malloc(sizeof(int*) * col);
  for (int i = 0; i < col; i++) {
    transposedMatrix[i] = malloc(sizeof(int) * row);
  }
  for (int i = 0; i < col; i++) {
    for (int j = 0; j < row; j++) {
      transposedMatrix[i][j] = matrix[j][i];
    }
  }
  return transposedMatrix;
}