L1 Supplementary Notes Page 1 Selection Sort Comparison Counting

L1 Supplementary Notes Page 2 Sum Principle

L1 Supplementary Notes Page 3 Sum Principle in Abstract Another notation for finite set: set of men in this section = {p|p is a male student in COMP 170 L2}

L1 Supplementary Notes Page 4 Matrix Multiplication

L1 Supplementary Notes Page 5 Product Principle Si and Sj are disjoint, |Si| = n S = S1 U S2 U … U Sm |S| = m |Si| = mn

L1 Supplementary Notes Page 6 2-element subsets and ordered pairs l Ordered pairs: (1, 2) and (2, 1) are different l {1, 2}  (1, 2), (2, 1) l {1, 3}  (1, 3), (3, 1) l …. l # of 2-subsets * 2 = number of ordered pairs

L1 Supplementary Notes Page 7 Number of Ordered Pairs l S1: pairs with first element =1 l S2: pairs with first element = 2 l.. l Sn: pairs with first element = n l Si and Sj are disjoint, |Si| = n-1 l S = total # of ordered pairs l S= S1 U S2 U … U Sn |S| = n|Si| = n(n-1)