字符串中字符的快速排序<通用>

 

- (NSString *)reorderString:(NSString *)originalStr{
	
	int length = [originalStr length];
	int sizeChar;
	if (length < 12) {
		sizeChar = length;
	}
	else {
		sizeChar = length;
	}


	unichar wordChar;
	char *wordsChar = (char *)malloc(sizeof(char)*length);
	//char *wordsUnichar;
	for (int i = 1; i <= length; i++) {
		wordChar = [originalStr characterAtIndex:(i-1)];
		wordsChar[i] = wordChar;
	}
	
	quickSort(wordsChar, 0, length);
	

	
	NSString* result = [[NSString alloc] initWithCString:wordsChar];
	free(wordsChar);
//	for(int j = 1; j <= length; j++) {
//		wordChar = wordsChar[j];
//		NSLog(@"%c", wordChar);
//		wordsChar[j] = 0;
//	}
	return result;
}

 

 

下面是快速排序：

 

#import "CommomUitl.h"


@implementation CommomUitl

void swapV(char *a, char *b){
	char temp;     
	temp = *a;     
	*a = *b;    
	*b = temp;
}

int partitions(char originalStr[], int low, int high){
	
	char temp= originalStr[low];
	int i=low,j=high; 
	while(i<j)   {      
		while( (originalStr[j] >= temp) && (i<j) ) 
			j--;      
		if(i<j)  {
			swapV(&originalStr[i], &originalStr[j]);
			i++;
		}      
		while( ( originalStr[i] <= temp ) && (i<j) )
			i++;      
		if(i<j)  {
			swapV(&originalStr[i], &originalStr[j]);
			j--;
		}   
	}    
	return i;
}

void quickSort(char originalStr[], int low, int high){
	
	int pos;     
	if(low < high) {        
		pos=partitions(originalStr,low,high);        
		quickSort(originalStr,low,pos-1);        
		quickSort(originalStr,pos+1,high);              
	}
}
@end

 

 

输入字符串"iteye"

则输出"eeity"

 

 

总结：注意点一，动态分配数组和手动释放

注意点二，数组下标是否越界，以及开始下标值

 

堆与栈

 

以数组的方式申请空间时，由系统管理，其作用域结束则释放；在内存中为连续的，以栈方式存在

malloc方式申请空间，由程序员自己控制；需自己手动free，否则一直存在内存中；在内存中以堆的形式存在，非连续。