低位优先的字符串排序相当于是对键索引计数方法的一个扩展，主要用于处理固定长度字符串，比如说手机号，固定电话，银行卡卡号，字符串的长度为N，从右向左开始进行每个键作为值开始遍历，实现比较简单:
-(void)lowSort:(NSMutableArray *)dataSource singleLength:(NSInteger)len
{NSInteger sourceCount=[dataSource count];NSInteger R=256;NSMutableArray *tempArr=[[NSMutableArray alloc]initWithCapacity:1];for (NSInteger i=0; i<sourceCount; i++) {[tempArr addObject:[NSNull null]];}for (NSInteger d=len-1; d>=0; d--) {NSMutableArray *count=[[NSMutableArray alloc]initWithCapacity:1];for (NSInteger i=0; i<R+1; i++) {[count addObject:[NSNumber numberWithInteger:0]];}//统计频率for (NSInteger i=0; i<sourceCount; i++) {NSString *str=[dataSource objectAtIndex:i];NSInteger charValue=[str characterAtIndex:d]-48;count[charValue+1]=[NSNumber numberWithInteger:[count[charValue+1] integerValue]+1];}for (NSInteger j=0; j<R; j++) {count[j+1]=[NSNumber numberWithInteger:[count[j] integerValue]+[count[j+1] integerValue]];}//将元素从上到下分类for (NSInteger m=0; m<sourceCount; m++) {NSString *str=[dataSource objectAtIndex:m];NSInteger charValue=[str characterAtIndex:d]-48;tempArr[[count[charValue] integerValue]]=dataSource[m];count[charValue]=[NSNumber numberWithInteger:[count[charValue] integerValue]+1];}//重新排序赋值for (NSInteger i=0; i<sourceCount; i++) {dataSource[i]=tempArr[i];}}
}
代码测试:
LSD *lsd=[[LSD alloc]init];NSMutableArray *dataSource=[[NSMutableArray alloc]initWithObjects:@"12345",@"23456",@"78901",@"89764",@"12345",@"45678",@"89794",@"89754",@"64532",@"69784",nil];[lsd lowSort:dataSource singleLength:7];[dataSource enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {NSLog(@"%@",obj);}];NSLog(@"技术交流群:%@",@"228407086");NSLog(@"博客园-FlyElephant:http://www.cnblogs.com/xiaofeixiang");
效果如下:
