Similarly , store suffix sums of elements at even and odd indices
for ( int i = N - 3 ; i >= 0 ; i -= 2 ) { suffix [ i ] = arr [ i ] + suffix [ i + 2 ] ; } for ( int i = N - 4 ; i >= 0 ; i -= 2 ) { suffix [ i ] = arr [ i ] + suffix [ i + 2 ] ; }