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spiral message - code practice - September 3, 2017
using System;
class Solution
{
public static int[] SpiralCopy(int[,] inputMatrix)
{
// your code goes here
if(inputMatrix == null || inputMatrix.GetLength(0) == 0 || inputMatrix.GetLength(1) == 0)
{
return new int[0];
}
var rows = inputMatrix.GetLength(0);
var columns = inputMatrix.GetLength(1);
var startRow = 0; //0
var startCol = 0; // 0
var endRow = rows - 1; // 3
var endCol = columns - 1; // 0
// 5
// 10
// 15
// 20
var spiral = new int[rows * columns]; // 4
var index = 0;
while(startRow <= endRow && startCol <= endCol ) // 0 <= 3, 0 <= 0
{
// four loops
// top row
for(var col = startCol; col <= endCol; col++) // 5
{
var visit = inputMatrix[startRow, col];
spiral[index] = visit;
index++;
}
// last column
for(var row = startRow + 1 ; row <= endRow; row++) // from 1 to 3 in row, 10, 15, 20
{
var visit = inputMatrix[row, endCol];
spiral[index] = visit;
index++;
}
// last row, check edge case: one row
for(var col = endCol - 1; col >= startCol && endRow > startRow; col --) // add one more condition
{
var visit = inputMatrix[endRow, col];
spiral[index] = visit;
index++;
}
// first column
for(var row = endRow - 1; row > startRow && endCol > startCol; row --) // add one more condition
{
var visit = inputMatrix[row, startCol];
spiral[index] = visit;
index++;
}
startRow ++;
endRow --;
startCol ++;
endCol --;
}
return spiral;
}
static void Main(string[] args)
{
var inputMatrix = new int[,]{{1}};
var result = SpiralCopy( inputMatrix);
Console.WriteLine(result[0]);
}
}
// 0, 0
// first row, 1 - 5,
// last column, second row to last row , 20 is in second iteration,
// last row, next to last column, 19 - 16
// first column, next to last row -> 6, 6 is next to first row
// start pointer 1, 1, start again 4 loops from 7
// edge case: if it is one row, we do not visit twice, one row, no two rows, left -> right
// edge case: if it is one column, we start from top to down
// one element ->
// while loop
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