4. What is meant by the optimal substructure property in the context of dynamic programming. Using the dynamic programming technique, devise an algorithm for finding the least cost way to convert a given string X to another string Y . The allowed operations are INSERT, DELETE, REPLACE, and COPY with costs of 2, 3, 4, and 1 respectively for each of the above operations. Show the recurrence relation and then write a memoized program. Finally, add enough steps to be able to print the solution.

Light travels at a speed of 186,000 miles a second. the distance light travels in a year is 5,865,690,000,000 miles/year 5,865,695,000,000 miles/year 58,656,950,000,000 miles/year 6,789,000,0000 miles/year

Select the correct answer. andy received a potentially infected email that was advertising products. andy is at risk of which type of security threat? a. spoofing b. sniffing c. spamming d. phishing e. typo-squatting

Write a program that prints the day number of the year, given the date in the form month-day-year. for example, if the input is 1-1-2006, the day number is 1; if the input is 12-25-2006, the day number is 359. the program should check for a leap year. a year is a leap year if it is divisible by 4, but not divisible by 100. for example, 1992 and 2008 are divisible by 4, but not by 100. a year that is divisible by 100 is a leap year if it is also divisible by 400. for example, 1600 and 2000 are divisible by 400. however, 1800 is not a leap year because 1800 is not divisible by 400.