public class Solution {

public int computeArea(int A, int B, int C, int D, int E, int F, int G, int H) {

if (!isValidRectangle(A, B, C, D) || !isValidRectangle(E, F, G, H))

return 0;

int rect1Area = (D - B) * (C - A);

int rect2Area = (H - F) * (G - E);

int totalArea = rect1Area + rect2Area - getOverLappedArea(A, B, C, D, E, F, G, H);

return totalArea;

}

private int getOverLappedArea(int A, int B, int C, int D, int E, int F, int G, int H) {

int xLength = getOverlappedLength(A, C, E, G);

int yLength = getOverlappedLength(B, D, F, H);

return xLength * yLength;

}

private int getOverlappedLength(int A, int B, int C, int D) {

// C---A----B---D

if (C <= A && B <= D && A <= B)

return B - A;

// A---C---D---B

if (A <= C && D <= B && C <= D)

return D - C;

// A---C---B---D

if (A <= C && B <= D && C <= B)

return B - C;

// C---A---D---B

if (C <= A && D <= B && A <= D)

return D - A;

return 0;

}

private boolean isValidRectangle(int A, int B, int C, int D) {

if (A > C || B > D)

return false;

else

return true;

}

}