puzzle

Given an array of characters which forms a sentence of words, give an efficient algorithm to reverse the order of the words (not characters) in it. Example input and output: >>> reverse_words("this is a string") 'string a is this' It should be O(N) time and O(1) space ( split() and pushing on / popping off the stack are not allowed). The puzzle is taken from here . Thomas Watnedal A solution in C/C++: void swap(char* str, int i, int j){ char t = str[i]; str[i] = str[j]; str[j] = t; } void reverse_string(char* str, int length){ for(int i=0; i<length/2; i++){ swap(str, i, length-i-1); } } void

I saw this question on Reddit, and there were no positive solutions presented, and I thought it would be a perfect question to ask here. This was in a thread about interview questions: Write a method that takes an int array of size m, and returns (True/False) if the array consists of the numbers n...n+m-1, all numbers in that range and only numbers in that range. The array is not guaranteed to be sorted. (For instance, {2,3,4} would return true. {1,3,1} would return false, {1,2,4} would return false. The problem I had with this one is that my interviewer kept asking me to optimize (faster O(n)

This is just something that has bothered me for the last couple of days, I don't think it's possible to solve but I've seen template magic before. Here goes: To get the number of elements in a standard C++ array I could use either a macro (1), or a typesafe inline function (2): (1) #define sizeof_array(ARRAY) (sizeof(ARRAY)/sizeof(ARRAY[0])) (2) template <typename T> size_t sizeof_array(const T& ARRAY){ return (sizeof(ARRAY)/sizeof(ARRAY[0])); } As you can see, the first one has the problem of being a macro (for the moment I consider that a problem) and the other one has the problem of not

First off, this question is ripped out from this question. I did it because I think this part is bigger than a sub-part of a longer question. If it offends, please pardon me. Assume that you have a algorithm that generates randomness. Now how do you test it? Or to be more direct - Assume you have an algorithm that shuffles a deck of cards, how do you test that it's a perfectly random algorithm? To add some theory to the problem - A deck of cards can be shuffled in 52! (52 factorial) different ways. Take a deck of cards, shuffle it by hand and write down the order of all cards. What is the