如何统计一个字符串中出现某字符的个数

//count times of specific charecter in c-string；

#include <iostream>

int count_char(const char * str, char ch );
int main()
{
	using namespace std;
	//char * string = "hello world!";
	char string[] = "hello world!";
	char ch;
	int count;
	cout << "Please enter the character you want to count:\n";
	cin >> ch;
	count = count_char(string, ch);
	cout << string << " contains " << count << " " << ch << endl;
	cin.get();
	cin.get();
	return 0;
	
}
 
int count_char( const char * str, char ch )  // 改进1：const
{
	unsigned int count = 0;
	char a = ch;
	while( *str != '\0' )    //空值字符的数字编码=0，所以也可以改写为：while（ *str ),这样的写法好像可读性不是很好
	{
		if ( *str == ch)
			count++;
		str++;
	}

	return count;
}