C language interview questions solution for freshers beginners placement tricky good pointers answers explanation operators data types arrays structures functions. Python Program for recursive binary search. Returns index of x in arr if present, else 1 def binarySearch arr, l, r, x Check base case if r l. Download String Concatenation program. Output of program Concatenate strings without strcat function. C program to concatenate strings without using library function. I have a binary file that resulted from a program written in Compaq Visual Fortran. How can I read specific lines and save them in an Excel sheet Learn how to use loops in C, including for, while and do while loops, with examples of each. Ten Ways to Check if an Integer Is a Power Of Two in CTo write a program to check if an integer is a power of two, you could follow two basic strategies check the number based on its decimal value, or check it based on its binary representation. The former approach is more human friendly but generally less efficient the latter approach is more machine friendly but generally more efficient. We will explore both approaches, comparing ten different but equivalent C functions. Decimal Based Approaches to Checking for Powers of Two. Decimal integers in C source code are converted to binary form, but technically you dont need to know that you can still treat them as decimal in the algorithms you write. The first six functions presented are based on that view. Divide by Two. This function implements the pencil and paper method of checking whether an integer is a power of two. It repeatedly divides x, the 3. It divides until either the quotient becomes 1, in which case x is a power of two, or the quotient becomes odd before reaching 1, in which case x is not a power of two. Power. Of. Two unsigned int x. While x is even and 1. Check All. This function hard codes the first 3. BhQxgIgXX4/hqdefault.jpg' alt='Binary Search Program In C Using While Loop' title='Binary Search Program In C Using While Loop' />OR expression. If x is a power of two less than 2,1. C semantics. If x is not a power of two or is 2. Power. Of. Two unsigned int x. Check Next Power. While PHP 4, PHP 5, PHP 7 while loops are the simplest type of loop in PHP. They behave just like their C counterparts. The basic form of a while statement is. Java Data Structures 2nd Edition End of the World Production, LLC. In computer science, binary search, also known as halfinterval search, logarithmic search, or binary chop, is a search algorithm that finds the position of a target. This function computes each power of two incrementally, quitting when x is less than or equal to the current power of two. Power. Of. Two unsigned int x. Of. Two 1. while power. Of. Two lt x power. Of. Two lt 2. 14. Of. Two 2. return x power. Of. Two. The hard coded constant for 2. Linear Search. This function is the same as the Check Next Power algorithm except that the powers of two are precomputed and stored in a table. Power. Of. Two unsigned int x. Of. Two3. 2. 1,2,4,8,1. Of. Twoexponent lt x exponent lt 3. Of. Twoexponent. Binary Search. This function does a binary search of powers of two stored in a table. Power. Of. Two unsigned int x. Of. Two3. 2. 1,2,4,8,1. APower. Of. Two. int interval 1. Start out at midpoint. APower. Of. Two 0. Special case makes binary search easier. APower. Of. Two 1. Of. Twoexponent interval 1. Of. Twoexponent. APower. Of. Two x powers. Of. Twoexponent. APower. Of. Two. Log Search. This function uses logarithms to determine if x is a power of two, put perhaps not in the way youd expect. The log in base 2 of x, or log. Mathematically, if n is an integer, then x is a power of two if n is not an integer, then x is not. But in a computer, when floating point calculations are used, things dont always work out this neatly see section Beware of Logarithms for more about this. In this case, the solution is to choose the two integral exponents that bound the logarithm and compare x to their corresponding powers of two x can only be a power of two if it matches one of the two. Since Visual C does not have a built in function for log. Power. Of. Two unsigned int x. APower. Of. Two. unsigned int powers. Of. Two3. 2. 1,2,4,8,1. APower. Of. Two 0. Nfs Most Wanted 2012 Full Version For Pc Highly Compressed. Log base 2. is. APower. Of. Two x powers. Of. Twoexponent. Of. Twoexponent1. APower. Of. Two. When the exponent is 3. OR expression will short circuit before trying to access the table out of bounds. Binary Based Approaches to Checking for Powers of Two. An arguably more direct way to check if an integer is a power of two is to access its binary representation. An unsigned integer is a power of two if and only if it has exactly one 1 bit. The four functions below are based on that observation. Count Ones. This function is probably the first that comes to mind counting 1 bits. Of course you dont need to count all 1 bits you can stop counting if more than one 1 bit is found. Power. Of. Two unsigned int x. Of. One. Bits 0. Of. One. Bits lt 1. Is the least significant bit a 1 Of. One. Bits. x 1 Shift number one bit to the right. Of. One. Bits 1 True if only one 1 bit. Shift Right. This function is the equivalent of the Divide by Two algorithm. Dividing a binary integer by 2 is the same as shifting it right one bit, and checking whether a binary integer is odd is the same as checking if its least significant bit is 1. Power. Of. Two unsigned int x. While x is even and 1. The only way the statement x 1 becomes true is when there is only one 1 bit in x to start with. Decrement and Compare. This function is a common one liner youll find on the Web, and is how the check is implemented in malloc. GNU C Library glibc. Power. Of. Two unsigned int x. There are two halves to the expression x 0 and x x 1. The first half makes 0 a special case, since the second half only works correctly for positive numbers. The second half the interesting part of the expression is true when x is a power of two and false when x is not. Lets see why. Let n be the position of the leftmost 1 bit if x. If x is a power of two, its lone 1 bit is in position n. This means x 1 has a 0 in position n. To see why, recall how binary subtraction works. When subtracting 1 from x, the borrow propagates all the way to position n bit n becomes 0 and all lower bits become 1. Now, since x has no 1 bits in common with x 1, x x 1 is 0, and x x 1 is true. Here are some examples Ill use 8 bit unsigned integers to keep things manageable If x is not a power of two, x 1 has a 1 in position n. This is because the borrow will not propagate to position n. Subtraction borrows from the lowest 1 bit, which by virtue of x not being a power of two, is before position n. The lowest 1 bit is like a firewall that prevents the borrow from reaching position n. Since x and x 1 have at least one 1 bit in common at position n x x 1 is nonzero, and x x 1 is false. Here are some examples 1. Complement and Compare. This function is another one liner that can be found on the Web. At its core, it is similar to the Decrement and Compare method. Power. Of. Two unsigned int x. The first half of the expression ensures that x is a positive integer. The second half of the expression, x x 1 x, is true only when x is a power of two. It compares x with its twos complement. The twos complement of x is computed with x 1, which inverts the bits of x and adds 1 x 1 is equivalent to x, but negation is technically illegal for an unsigned integer. Let n be the position of the leftmost 1 bit if x. If x is a power of two, its lone 1 bit is in position n. This means x has a 0 in position n and 1s everywhere else. When 1 is added to x, all positions below n become 0 and the 0 at position n becomes 1. In other words, the carry propagates all the way to position n. So what happens is this negating x inverts all its bits, but adding 1 inverts them back, from position n on down. So, x x 1 x is true. Here are some examples If x is not a power of two, x has at least one 0 below position n. When 1 is added, the carry will not propagate to position n. In other words, not all bits from position n and below will be inverted back. This means x x 1 x is false. Here are some examples Endianness. In case you were wondering, these algorithms are endian independent. Integers are accessed numerically and logically with arithmetic, bitwise, and logical operators, not as byte strings. Comparing the Algorithms.
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