ProjectEuler-Java/Sol15.java at master · JoshP/ProjectEuler-Java · GitHub

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import java.math.*;

public class Sol15 extends BaseSolution {

public void runSolution() {

int gridSize = 20;

Long[][] countArray = new Long[gridSize + 1][gridSize + 1];

System.out.println(findRoutes(0, 0, gridSize, countArray));

}

public long findRoutes(int x, int y, int max, Long[][] countArray) {

if (x == max && y == max) {

return 1;

}

if (countArray[x][y] != null) {

return countArray[x][y];

}

long count = 0;

if (x < max) {

count += findRoutes(x + 1, y, max, countArray);

}

if (y < max) {

count += findRoutes(x, y + 1, max, countArray);

}

countArray[x][y] = count;

return count;

}