// 1.去除字符串中的字符串和回车
    NSString *string = @"  \n   I Love China ";
    NSLog(@"原始字符串%@",string);
    
    //去掉字符串两端空格
    NSString *str1 = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    NSLog(@"去掉字符串两端空格%@",str1);
    
    //去掉字符串两端空格和回车
    NSString *str2 = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet ]];
    NSLog(@"去掉字符串两端空格和回车%@",str2);
    
    //去掉字符串中的空格和回车
    NSMutableString *mutStr = [NSMutableString stringWithString:string];
    
    NSRange range = {0,string.length};
    [mutStr replaceOccurrencesOfString:@" " withString:@"" options:NSLiteralSearch range:range];
    NSRange range2 = {0,mutStr.length};
    
    [mutStr replaceOccurrencesOfString:@"\n"withString:@""options:NSLiteralSearch range:range2];
    NSLog(@"去掉字符串中的空格和回车%@",mutStr);




//  2.iOS开发之判断数组中是否有重复元素

// 方法一：
 NSMutableDictionary *dic = [NSMutableDictionary dictionary];
for (NSNumber *number in arr) {
    [dic setObject:number forKey:number];
}
NSLog(@"[dic allValues] %@",[dic allValues]);

// 方法二：
NSArray *arr = @[@1,@2,@1];
NSSet *set = [NSSet setWithArray:arr];
// [set allObjects]得到的是数组
NSArray *newArr = [set allObjects];
NSLog(@"newArr:  %@", newArr);