H04 Midterm Practice

The new value is copied from the memory pointed to by

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Unformatted text preview: e, 0, NULL); return csv; } /* Function: CSVSetNth * Usage: CSVSetNth(csv, 22, &val); * -------------------------------* Sets the given value at the index, replacing any previous * value. The new value is copied from the memory pointed to * by valueAddr. !Valid indexes are [0, maxIndex]; an error * is raised if index is out of bounds. */ void CSVSetNth(CSparseVector *csv, int index, void *valueAddr) Problem 3: Numbers and bits a) The CS106 RandomInteger function returns a value randomly chosen from the range [low, high]. It is implemented on top of the C stdlib function r and that returns an unsigned int in the range [0, RAND_MAX]. R AND_MAX is equal to U INT_MAX , i.e. the largest representable unsigned int. RandomInteger is designed to map the result from rand onto the desired range. The code is shown below. int RandomInteger(int low, int high) { double d = rand() / ((double) RAND_MAX + 1); // map onto [0, 1) int k = (int) (d * (high - low + 1)); // scale/truncate return (low + k); // translate } The first line maps the rand result onto the range [0, 1) as a double. Would this code work equally well using float instead of double? Explain why or why not. The above function has been used by thousands of students for over 15 years. Imagine my surprise when a student recently showed me that it did not work correctly for very –4– large ranges. Trace the operation of RandomInteger(0, INT_MAX). What is returned? Describe how to change the code to make...
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This note was uploaded on 02/06/2014 for the course CS 106X taught by Professor Cain,g during the Winter '08 term at Stanford.

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