private bool IsBetterValidResult(TriangleMaxSumPathResult currentResult, int currentValue,
TriangleMaxSumPathResult proposedResult, int proposedValue)
{
if (proposedResult.MaxSum == null)
{
return(false);
}
if (!HaveDifferentParity(currentValue, proposedValue))
{
return(false);
}
if (currentResult.MaxSum == null)
{
return(true);
}
if (currentResult.MaxSum < proposedResult.MaxSum + currentValue)
{
return(true);
}
return(false);
}
// Solution explained in README.MD
public TriangleMaxSumPathResult Calculate(int[] input)
{
var inputTriangle = new Triangle <int>(input);
var resultTriangle = CreateResultsTriangle(input.Length);
// we initialize bottom values with obvious results
var row = inputTriangle.Height - 1;
for (int column = 0; column <= row; column++)
{
var currentValue = inputTriangle[row, column];
resultTriangle[row, column] = new TriangleMaxSumPathResult(currentValue);
}
// we fill parents with results
for (row--; row >= 0; row--)
{
for (int column = 0; column <= row; column++)
{
var leftChildResult = resultTriangle[row + 1, column];
var rightChildResult = resultTriangle[row + 1, column + 1];
var currentValue = inputTriangle[row, column];
var leftChildValue = inputTriangle[row + 1, column];
var rightChildValue = inputTriangle[row + 1, column + 1];
TriangleMaxSumPathResult bestResult = new TriangleMaxSumPathResult();
if (IsBetterValidResult(bestResult, currentValue, leftChildResult, leftChildValue))
{
bestResult = leftChildResult.AppendValue(currentValue);
}
if (IsBetterValidResult(bestResult, currentValue, rightChildResult, rightChildValue))
{
bestResult = rightChildResult.AppendValue(currentValue);
}
resultTriangle[row, column] = bestResult;
}
}
// we return top result
return(resultTriangle[0, 0]);
}
private Triangle <TriangleMaxSumPathResult> CreateResultsTriangle(int length)
{
var array = new TriangleMaxSumPathResult[length];
return(new Triangle <TriangleMaxSumPathResult>(array));
}
