Sword finger offer 29 Print matrix clockwise

Title Description ：

Enter a matrix , Print out each number in a clockwise order from the outside in .

Topic analysis ：

Print in clockwise order , Then we can divide it into four steps ：

1. From left to right

2. From the top down

3. From right to left

4. From bottom to top

Therefore, we can express the row or column of the four edges of the matrix respectively .

After each printing, we print the row or column in which it is located +-1, Used to reduce the matrix , To show that we have gone through this section .

The code is as follows ：

int* spiralOrder(int** matrix, int matrixSize, int* matrixColSize, int* returnSize){

     if(matrixSize==0){
         *returnSize=0;
         return NULL;
     }
     *returnSize=matrixSize*(*matrixColSize);// Find the number of elements in the matrix 
     int up=0,down=matrixSize-1;// Four borders 
     int left=0,right=*matrixColSize-1;
     int*ret=(int*)malloc(sizeof(int)*(*returnSize));// Construct an array 
     int index=0;
     while(index<*returnSize){
          for(int i=left;index<*returnSize&&i<=right;i++){// From the left -> Right 
              ret[index++]=matrix[up][i];
          }
          up++; // Reduce the matrix 
          for(int i=up;index<*returnSize&&i<=down;i++){// From above -> Next 
              ret[index++]=matrix[i][right];
          }
          right--;
          for(int i=right;index<*returnSize&&i>=left;i--){// From the right -> Left 
              ret[index++]=matrix[down][i];
          }
          down--;
          for(int i=down;index<*returnSize&&i>=up;i--){// From below -> On 
              ret[index++]=matrix[i][left];
          }
          left++;
     }
     return ret;
}