Adt lab/pointers - ประวัติรุ่นแก้ไข

Jittat: /* Finding string length */

2015-08-28T03:51:05Z

Finding string length

2015-08-28T03:47:51Z

How to read strings

2015-08-28T03:46:27Z

How to read strings

2015-08-28T02:25:24Z

Dynamic memory allocations

2015-08-28T02:24:56Z

Dynamic memory allocations

2015-08-28T02:22:58Z

Dynamic memory allocations

2015-08-27T23:26:11Z

Pointers and arrays

2015-08-27T23:25:45Z

Strings and arrays of characters

2015-08-27T23:25:18Z

Arrays are not pointers

2015-08-27T23:23:40Z

Arrays are not pointers

←รุ่นแก้ไขก่อนหน้า		รุ่นแก้ไขเมื่อ 03:51, 28 สิงหาคม 2558
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	=== Finding string length ===		=== Finding string length ===
		+	The following code read a string with <tt>cin.getline</tt> and find the string length.
		+
		+	<source lang="cpp">
		+	#include <iostream>
		+	using namespace std;
		+
		+	int string_len(char* st)
		+	{
		+	int len = 0;
		+	while(*st != '\0') {
		+	len++;
		+	st++;
		+	}
		+	return len;
		+	}
		+
		+	main()
		+	{
		+	char st[1000];
		+	int l;
		+
		+	cin.getline(st,1000);
		+	l = string_len(st);
		+
		+	cout << l << endl;
		+	}
		+	</source>

	== Other links ==		== Other links ==

←รุ่นแก้ไขก่อนหน้า		รุ่นแก้ไขเมื่อ 03:47, 28 สิงหาคม 2558
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	This function <tt>cin.getline(s,n)</tt> reads a string and write to an array <tt>s</tt> for at most <tt>n</tt> characters. The limit <tt>n</tt> prevents the function from overwrite the array.		This function <tt>cin.getline(s,n)</tt> reads a string and write to an array <tt>s</tt> for at most <tt>n</tt> characters. The limit <tt>n</tt> prevents the function from overwrite the array.
		+
		+	=== Finding string length ===

	== Other links ==		== Other links ==

←รุ่นแก้ไขก่อนหน้า		รุ่นแก้ไขเมื่อ 03:46, 28 สิงหาคม 2558
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	=== How to read strings ===		=== How to read strings ===
		+	In C++, you can use <tt>string</tt> type to keep strings, and, as usual, you can use <tt>cin</tt> to read it.
		+
		+	<source lang="cpp">
		+	string st;
		+	cin >> st;
		+	</source>
		+
		+	Standard <tt>string</tt> class provides many important string operations.
		+
		+	However, in our practice, we want you to work with arrays of characters. Therefore, we will use <tt>cin.getline</tt>.
		+
		+	<source lang="cpp">
		+	char st[1000];
		+	cin.getline(st,1000);
		+	</source>
		+
		+	This function <tt>cin.getline(s,n)</tt> reads a string and write to an array <tt>s</tt> for at most <tt>n</tt> characters. The limit <tt>n</tt> prevents the function from overwrite the array.

	== Other links ==		== Other links ==

@@ แถว 273: / แถว 273: @@
 </source>
-You have to deallocate the memory that you allocate to the system after you finish using it using the <tt>free</tt> statement.  If you do not free the allocated memory, you might face "memory leak" problems.
+You have to deallocate the memory that you allocate to the system after you finish using it using the <tt>delete</tt> operator.  If you do not free the allocated memory, you might face "memory leak" problems.
 To deallocate:

@@ แถว 278: / แถว 278: @@
 <source lang="cpp">
-   free p;
+   delete p;
-   free q;
+   delete q;
 </source>

←รุ่นแก้ไขก่อนหน้า		รุ่นแก้ไขเมื่อ 02:22, 28 สิงหาคม 2558
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	== Dynamic memory allocations ==		== Dynamic memory allocations ==
		+	There are two ways to allocate memory. In C, you will use standard library: <tt>malloc</tt> and other related functions. In C++, there is a simpler way to allocate using the <tt>new</tt> operator.
		+
		+	<source lang="cpp">
		+	int* p = new int;
		+	double* q = new double;
		+	</source>
		+
		+	You have to deallocate the memory that you allocate to the system after you finish using it using the <tt>free</tt> statement. If you do not free the allocated memory, you might face "memory leak" problems.
		+
		+	To deallocate:
		+
		+	<source lang="cpp">
		+	free p;
		+	free q;
		+	</source>

	== Strings and arrays of characters ==		== Strings and arrays of characters ==

@@ แถว 264: / แถว 264: @@
    *p = 0;     // compiles OK, but usually causes problems when running
 </source>
 == Strings and arrays of characters ==

@@ แถว 277: / แถว 277: @@
   s[5]: '\0'
   s[6]: undefined
 == Other links ==

@@ แถว 255: / แถว 255: @@
    p = b;     // OK
    a = b;     // NOT OK
 </source>

←รุ่นแก้ไขก่อนหน้า		รุ่นแก้ไขเมื่อ 23:23, 27 สิงหาคม 2558
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	=== Arrays are not pointers ===		=== Arrays are not pointers ===
		+	Although we can use pointers and arrays interchangeably in many cases. They are not the same. Notably, you cannot assign new locations to an array.
		+
		+	<source lang="cpp">
		+	int a[100];
		+	int b[10];
		+	int* p;
		+
		+	p = a; // OK
		+	p = b; // OK
		+	a = b; // NOT OK
		+	</source>

	== Strings and arrays of characters ==		== Strings and arrays of characters ==