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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:
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原文地址：http://www.cnblogs.com/xiaofeixiang/p/4855578.html
