1. 从字符串“123-456-789-000”中提取数字部分，组成新的输出字符串

NSString *str=[[NSString alloc]initWithFormat:@"123-456-789-000"];        NSArray *arr=[str componentsSeparatedByString:@"-"];        NSLog(@"%@%@%@%@",[arr objectAtIndex:0],[arr objectAtIndex:1],[arr objectAtIndex:2],[arr objectAtIndex:3]);        NSString *newStr=[str stringByReplacingOccurrencesOfString:@"-" withString:@""];        NSLog(@"%@",newStr);

2. 将四个十进制三位数添加到数组中，按从小到大排序后组成新的数组

#import         int main(int argc, const char * argv[]) {          @autoreleasepool {            NSMutableArray *arr=[[NSMutableArray alloc]initWithObjects:@"123",@"234",@"110",@"142", nil];            for(int i=0;i<[arr count]-1;i++){              for(int j=0;j<[arr count]-i-1;j++){                NSComparisonResult result=[[arr objectAtIndex:j] compare:[arr objectAtIndex:j+1]];                if(result==NSOrderedDescending){                  [arr exchangeObjectAtIndex:j+1 withObjectAtIndex:j];                }              }            }            for(int i=0;i<[arr count];i++){              NSLog(@"%@",[arr objectAtIndex:i]);            }          }          return 0;        }