The final diff array should be like this:

100 100 0 0 -100 (straight foward from the code)

So when you iterate over it to get the accumalated sum you'll get this:

iteration		value of x	accumulated sum
0			0		0
1			100		100
2			100		200	
3			0		200
4			0		200
5			-100		100

The maximum value of the accumulated sum is 200.