containing only three types of characters: '(', ')' and '*', return true if s is valid. The following rules define a valid string: Any left parenthesis '(' must have a corresponding right parenthesis ')'. Any right parenthesis ')' must have a corresponding left parenthesis '('. Left parenthesis '(' must go before the corresponding right parenthesis ')'. '*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string "".   Example 1: Input: s = "()" Output: true.

(Conversion) Write a C++ program that converts gallons to liters. The program should display gallons from 10 to 20 in 1-gallon increments and the corresponding liter equivalents. Use the relationship that 1gallon=3.785liters.

(Modify) Rewrite the following programs to conform to good programming practice and correct syntax: a. #include using namespace std; int main( ){ cout << “The time has come” ; return 0;} b. #include using namespace std; int main ( ){cout << “Newark is a city\n”;cout << “in New Jersey\n”; cout << “It is also a city\n” ; cout << “in Delaware\n” ; return 0;} c. #include using namespace std; int main() {cout << Reading a program\n”;cout << “is much easier\n” ; cout << “if a standard form for main is used\n” ; cout <<“and each statement is written\n”;cout << “on a line by itself\n” ; return 0;} d. #include using namespace std; int main ( ){ cout << “Every C++ program” ; cout <<“\nmust have one and only one” ; cout << “main function” ; cout << “\n The escape sequence of characters”) ; cout << “\nfor a newline can be placed anywhere” ; cout <<“\n in the message passed to cout” ; return 0;}

(Conversion) a. Write a C++ program to convert meters to feet. The program should request the starting meter value, the number of conversions to be made, and the increment between metric values. The display should have appropriate headings and list the meters and the corresponding feet value. If the number of iterations is greater than 10, have your program substitute a default increment of 10. Use the relationship that 1 meter = 3.281 feet. b. Run the program written in Exercise 6a on a computer. Verify that your program begins at the correct starting meter value and contains the exact number of conversions specified in your input data. c. Modify the program written in Exercise 6a to request the starting meter value, the ending meter value, and the increment. Instead of the condition checking for a fixed count, the condition checks for the ending meter value. If the number of iterations is greater than 20, have your program substitute a default increment of (ending value - starting value) / 19.

When you borrow money to buy a house, a car, or for some other purpose, you repay the loan by making periodic payments over a certain period of time. Of course, the lending company will charge interest on the loan. Every periodic payment consists of the interest on the loan and the payment toward the principal amount. To be specific, suppose that you borrow $1,000 at an interest rate of 7.2% per year and the payments are monthly. Suppose that your monthly payment is $25. Now, the interest is 7.2% per year and the payments are monthly, so the interest rate per month is 7.2/12 = 0.6%. The first months interest on $1,000 is 1000 0.006 = 6. Because the payment is $25 and the interest for the first month is $6, the payment toward the principal amount is 25 6 = 19. This means after making the first payment, the loan amount is 1,000 19 = 981. For the second payment, the interest is calculated on $981. So the interest for the second month is 981 0.006 = 5.886, that is, approximately $5.89. This implies that the payment toward the principal is 25 5.89 = 19.11 and the remaining balance after the second payment is 981 19.11 = 961.89. This process is repeated until the loan is paid. Write a program that accepts as input the loan amount, the interest rate per year, and the monthly payment. (Enter the interest rate as a percentage. For example, if the interest rate is 7.2% per year, then enter 7.2.) The program then outputs the number of months it would take to repay the loan. (Note that if the monthly payment is less than the first months interest, then after each payment, the loan amount will increase. In this case, the program must warn the borrower that the monthly payment is too low, and with this monthly payment, the loan amount could not be repaid.)