dynamic programming: i rephrase the question

[Randall Twede]

i am trying to solve Euler81. it is very similar to Euler67. the only differences is 67 is a triangle and 81 is a square, and 67 wants maximum while 81 wants minimum.
i get the correct answer to 67, but for 81 i get 409646 when the correct answer is apparently 427337.
i thought i was using the same approach for both.
67

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

class Euler67 implements Problem
{
	int[][] data = new int[100][];
	
	public String solve()
	{
		try
		{
			readData();
			for(int i = 98; i >= 0; i--)
			{
				for(int j = 0; j < data[i].length; j++)
				{
					data[i][j] = data[i][j] + Math.max(data[i + 1][j], data[i + 1][j + 1]);
				}
			}
			return Integer.toString(data[0][0]);
		}
		catch(IOException e)
		{
			return("error: IOException");
		}
	}
	
	public String getMessage()
	{
		return "Find the maximum sum travelling from the top of the triangle to the base.";
	}
	
	private void readData() throws IOException
	{
		BufferedReader bufferedReader = new BufferedReader(new FileReader("triangle.txt"));
		for (int i = 0; i < 100; i++)
		{
			data[i] = new int[i + 1];
			String[] values = bufferedReader.readLine().split(" ");
			for (int j = 0; j <= i; j++)
			{
				data[i][j] = Integer.parseInt(values[j]);
			}
		}
	}
}

81

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

class Euler81 implements Problem
{
	final int size = 80;
	int[][] data = new int[size][size];
	
	public String solve()
	{
		try
		{
			readData();
			//System.out.println(data[79][79]);
			for(int i = size - 2; i >= 0; i--)
			{
				//System.out.println(data[i][size - 1]);
				data[i][size - 1] = data[i][size - 1] + data[i + 1][size - 1];	//last column
				//System.out.println(data[i][size - 1]);
				//System.out.println(data[size - 1][i]);
				data[size - 1][i] = data[size - 1][i] + data[size - 1][i + 1];	//last row
				//System.out.println(data[size - 1][i]);
			}
			//System.out.println(data[0][0]);
			for(int i = size - 2; i >= 0; i--)
			{
				data[i][i] = data[i][i] + Math.min(data[i][i+1], data[i + 1][i]);
				//System.out.println(data[i][i]);
				for(int j = i - 1; j >= 0; j--)
				{
					data[i][j] = data[i][j] + Math.min(data[i + 1][j], data[j + 1][i]);
					data[j][i] = data[j][i] + Math.min(data[i + 1][j], data[j + 1][i]);
				}
			}
			//System.out.println(data[0][0]);
			//System.out.println(data[0][1]);
			//System.out.println(data[1][0]);
			return Integer.toString(data[0][0]);	//427337
		}
		catch(IOException e)
		{
			return("error: IOException");
		}
	}
	
	public String getMessage()
	{
		return "Find the minimal path sum from the top left to the bottom right by moving right and down.";
	}
	
	private void readData() throws IOException
	{
		BufferedReader bufferedReader = new BufferedReader(new FileReader("matrix.txt"));
		for (int i = 0; i < size; i++)
		{
			String[] values = bufferedReader.readLine().split(",");
			for (int j = 0; j < size; j++)
			{
				data[i][j] = Integer.parseInt(values[j]);
			}
		}
	}
}

[Randall Twede]

solved it finally.
for(int j = i - 1; j >= 0; j--)
{
data[i][j] = data[i][j] + Math.min(data[i + 1][j], data[j + 1][i]);
data[j][i] = data[j][i] + Math.min(data[i + 1][j], data[j + 1][i]);
}
should have been
for(int j = i - 1; j >= 0; j--)
{
data[i][j] = data[i][j] + Math.min(data[i + 1][j], data[i][j + 1]);
data[j][i] = data[j][i] + Math.min(data[j + 1][i], data[j][i + 1]);
}
as with all the dynamic programming solutions i have seen so far it is quite simple, elegant, and fast.