Description
Question 1 [15 points].
Write a function that gets two ints x and y, and returns the sum of all ints between x and y,
including them.
int sum_interval(int x, int y);
For example:
– sum_interval(1, 4)returns 1+2+3+4=10.
– sum_interval(10, 3)returns 3+4+5+6+7+8+9+10=52.
– sum_interval(2, -1)returns (-1)+0+1+2=2.
– sum_interval(-1, -1)returns -1.
1. Note that we may have x>=y or x<=y. 2. You may assume that the sum will be within the range of int. Question 2 [15 points]. Write a function that gets a string str, changes all lower case letters to * (asterisk), and all upper case letters to $ (dollar sign). All other characters remain unchanged. The function returns the total number of letters modified. int hide_letters(char* str); For example: – If str is “12ab0”, then the function changes it to “12**0”, and returns 2. – If str is “aBCDe*”, then the function changes it to “*$$$**”, and returns 5. – If str is “0123&***”, then the function keeps the string as is, and returns 0. – An empty string is also a string. Question 3 [20 points]. Implement the function that gets an array of ints of length n, and returns the number of times the maximal element appears in the array. You may assume that n>0.
int count_max(const int* arr, int n);
For example:
– On input [1,7,-3,7,4,7] the function returns 3 because 7 appears three times.
– On input [-2,-3,-3] the function returns 1 because -2 appears once.
– On input [111] the function returns 1 because 111 appears once.
Question 4 [35 points].
Write a function that gets a string representing a positive integer and an int between 0 and 9.
The function multiplies that two numbers and returns the result in a string.
char* mult_number_by_digit(const char* num, int digit);
For example:
– mult_number_by_digit(“12340”, 6) returns “74040”.
– mult_number_by_digit(“9”, 0) returns “0”.
– mult_number_by_digit(“8”, 1) returns “8”.
– mult_number_by_digit(“9999999999999”, 3) returns “29999999999997”.
1. You may assume that the input is always legal, i.e., the string is a positive integer
correctly formatted, and 0 <= digit <= 9. Assume there are no unnecessary leading zeros, etc. 2. Note that the numbers may be so large that they do not fit into 4 bytes or 8 bytes. That is, you should not try to convert string to int. 3. Remember to use malloc appropriately and return the string allocated on the heap. Question 5 [15 points]. Write a function that gets an array of n ints, where each entry in the array is between 0 and 9. The function multiplies all these numbers and outputs the result as a string. The reason it needs to output a string (and not an int) is because the result might be too large to fit into an int/long. You may assume that n>0.
char* mult_digits(const int* digits, int n);
For example:
– mult_digits([3], 1) returns “3”.
– mult_digits([9,9], 2) returns “81”.
– mult_digits([5,5,4,5,5], 5) returns “2500”.
– mult_digits([1,2,2,2,1,2,4,4,2,2], 10) returns “1024”.
– mult_digits([9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9], 20) returns
“12157665459056928801”.
1. You may assume that the input is always legal, i.e., 0 <= digit[i] <= 9 for all i=0…n-1.
2. Remember to use malloc appropriately and return the string allocated on the heap.
3. If you are allocating memory for some intermediate calculations, remember to free it
before returning to avoid memory leaks.
