ALGORITHMS AND FLOWCHARTS, Study notes of Data Structures and Algorithms

Download ALGORITHMS AND FLOWCHARTS and more Study notes Data Structures and Algorithms in PDF only on Docsity! n ALGORITHMS AND | FLOWCHARTS Vi ALGORITHMS AND FLOWCHARTS • A typical programming task can be divided into two phases: • Problem solving phase • produce an ordered sequence of steps that describe solution of problem • this sequence of steps is called an algorithm • Implementation phase • implement the program in some programming language PSEUDOCODE & ALGORITHM Pseudocode: • Input a set of 4 marks • Calculate their average by summing and dividing by 4 • if average is below 50 Print “FAIL” else Print “PASS” PSEUDOCODE & ALGORITHM • Detailed Algorithm • Step 1: Input M1,M2,M3,M4 Step 2: GRADE  (M1+M2+M3+M4)/4 Step 3: if (GRADE < 50) then Print “FAIL” else Print “PASS” endif THE FLOWCHART • (Dictionary) A schematic representation of a sequence of operations, as in a manufacturing process or computer program. • (Technical) A graphical representation of the sequence of operations in an information system or program. Information system flowcharts show how data flows from source documents through the computer to final distribution to users. Program flowcharts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flowchart. EXAMPLE PRINT “PASS” Step 1: Input M1,M2,M3,M4 Step 2: GRADE  (M1+M2+M3+M4)/4 Step 3: if (GRADE <50) then Print “FAIL” else Print “PASS” endif START Input M1,M2,M3,M4 GRADE(M1+M2+M3+M4)/4 IS GRADE<5 0 PRINT “FAIL” STOP YN EXAMPLE 2 • Write an algorithm and draw a flowchart to convert the length in feet to centimeter. Pseudocode: • Input the length in feet (Lft) • Calculate the length in cm (Lcm) by multiplying LFT with 30 • Print length in cm (LCM) EXAMPLE 2 Algorithm • Step 1: Input Lft • Step 2: Lcm  Lft x 30 • Step 3: Print Lcm START Input Lft Lcm  Lft x 30 Print Lcm STOP Flowchart EXAMPLE 4 •Write an algorithm and draw a flowchart that will calculate the roots of a quadratic equation • Hint: d = sqrt ( ), and the roots are: x1 = (–b + d)/2a and x2 = (–b – d)/2a 2 0ax bx c   2 4b ac EXAMPLE 4 Pseudocode: • Input the coefficients (a, b, c) of the quadratic equation • Calculate d • Calculate x1 • Calculate x2 • Print x1 and x2 EXAMPLE 4 •Algorithm: • Step 1: Input a, b, c • Step 2: d  sqrt ( ) • Step 3: x1  (–b + d) / (2 x a) • Step 4: x2  (–b – d) / (2 x a) • Step 5: Print x1, x2 4b b a c    START Input a, b, c d  sqrt(b x b – 4 x a x c) Print x1 ,x2 STOP x1 (–b + d) / (2 x a) X2  (–b – d) / (2 x a) IF–THEN–ELSE STRUCTURE • The structure is as follows If condition then true alternative else false alternative endif IF–THEN–ELSE STRUCTURE • The algorithm for the flowchart is as follows: If A>B then print A else print B endif is A>B Print BPrint A Y N RELATIONAL OPERATORS Relational Operators Operator Description > Greater than < Less than = Equal to  Greater than or equal to  Less than or equal to  Not equal to NESTED IFS • One of the alternatives within an IF–THEN–ELSE statement • may involve further IF–THEN–ELSE statement EXAMPLE 6 • Write an algorithm that reads three numbers and prints the value of the largest number. EXAMPLE 6 Step 1: Input N1, N2, N3 Step 2: if (N1>N2) then if (N1>N3) then MAX  N1 [N1>N2, N1>N3] else MAX  N3 [N3>N1>N2] endif else if (N2>N3) then MAX  N2 [N2>N1, N2>N3] else MAX  N3 [N3>N2>N1] endif endif Step 3: Print “The largest number is”, MAX