http:^^www.cs.cornell.edu^info^courses^current^cs100b^info5.html
来自「This data set contains WWW-pages collect」· HTML 代码 · 共 133 行
HTML
133 行
MIME-Version: 1.0
Server: CERN/3.0
Date: Sunday, 24-Nov-96 22:46:43 GMT
Content-Type: text/html
Content-Length: 2963
Last-Modified: Friday, 15-Nov-96 18:02:45 GMT
<html><head><title>CS100B Program 5 Clarifications</title></head><body><h2><center>CS100B Program 5 Clarifications</center></h2><h3><center>14 November 1996</center></h3><hr><h4>Added: 13 November 1996</h4><h2>Part 4</h2>Part 4 asks you to compare the running time of Parts 2 and 3. Unfortunately,since we're sorting only 256 elements, both parts execute in less than asecond. So, for Part 4, answer this question: Which part (2 or 3) shouldexecute faster? Why?<hr><h4>Added: 13 November 1996</h4><h2>make_array_3</h2>In <strong>make_array_3</strong>, I say that it has one argument,<strong>array</strong>. Then, in the function, it refers to <strong>a</strong>.These should be the same. So, the function should be:<pre>void make_array(elemptr a[256]){int i;for (i = 0; i < 256; i++) { a[i] = (elemptr)malloc(sizeof(elem)); if (a[i] == NULL) { printf("Error: out of memory at %d\n", i); exit(1); } a[i]->x = rand() % 99 + 1; }}</pre><hr><h4>Added: 8 November 1996</h4><h2>Mac Memory Limits</h2>Macs have a memory limit that you can statically declare only 32k bytes ofdata. As a result, we have to change the number of things that you have tosort.<p><h3>Part 1</h3>Each int is 4 bytes, so 32k should be able to fit 8k ints. However, we needa little room for additional stuff (like function calls, which take upmemory), so we'll only sort 4096 integers. For the output, print every 64thinteger, 8 per line.<p>Only the size of the array in <strong>make_array_1</strong> changes.<p><h3>Part 2</h3>Each elem is 1k bytes, so we could only fit 32. As a result, we'lldynamically allocate the array. You don't know how to do this, so I'llgive you the code. We will sort an array of 256 elems, printing every 4thfor output. Change <strong>make_array_2</strong> to:<pre>void make_array_2(elem **a){int i;*a = (elem *)malloc(256 * sizeof(elem));if (*a == NULL) { printf("Error: out of memory!\n"); exit(1); }for (i = 0; i < 256; i++) (*a)[i].x = rand() % 99 + 1;}</pre>Also, your <strong>main</strong> should be:<pre>void main(void){elem *a;make_array_2(&a);/* you add the rest of the code */}</pre>Recall the array/pointer duality presented in class. "a" is a pointer to anelem. However, we dynamically allocated an array for "a" to point to. As aresult, "a[0]" is the first element of that array, and "a[255]" is the lastelement. In your quicksort function, you can treat "a" as though it was anarray of elems.<p><h3>Part 3</h3>We will sort an array of 256 pointers to elems, printing every 4thfor output. Only the size of the array in <strong>make_array_3</strong> changes.<p><hr><h4>Added: 7 November 1996</h4><h2>Partitioning Example</h2>There is a <em>very</em> minor typo in the partitioning example. On page 3,in the third line, it says "However, since l < r...". This should be "r < l".</body></html>⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?