关于NSString的练习题

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//1.现有如下定义的字符串： NSMutableString * str=@“iphoneAndroid”,能不能对该字符串进行修改，如果能，请输出删除Android后的新字符串。
NSMutableString *str=[NSMutableString stringWithCapacity:2];//创建一个可变的字符串
[str appendString:@"iphoneAndroid"];//往字符串里赋值
NSRange r={6,7};//截取字符串
[str deleteCharactersInRange:r];//删除字符串
NSLog(@"new str string id=%@",str);//输出字符串
第二种方法
NSMutableString *str=[[NSMutableString alloc]initWithString:@"iphoneAndroid"];//创建可变字符串并赋值
[str deleteCharactersInRange:NSMakeRange(6, 7)];//删除从下标是6的位置，长度是7的字符串
NSLog(@"%@",str);
//2求字符串“158”和“39”按十进制数值做差后的结果以字符串形式输出
NSMutableString *str1=[NSString stringWithFormat:@"%@",@"158"];//定义字符串
NSMutableString *str2=[NSString stringWithFormat:@"%@",@"39"];
int a=[str1 intValue];//把字符串转换成 int型
int b=[str2 intValue];
NSMutableString *str3=[NSMutableString stringWithFormat:@"%d",(a-b)];//（a-b）结果在格式化成字符串赋给str3
NSLog(@"results:%@",str3);
第二种方法
NSMutableString *str1=[[NSMutableString alloc]initWithString:@"158"];
NSMutableString *str2=[[NSMutableString alloc]initWithString:@"39"];
int a=[str1 intValue];
int b=[str2 intValue];
NSMutableString *str3=[NSMutableString stringWithFormat:@"%d",(a-b)];
NSLog(@"%@",str3);
//3取出符串“123-456-789-000”中的数字部分，组成一个新的字符串输出，（提示：可变字符串；返回数组）
第一种方法
NSMutableString *str4=[NSMutableString stringWithCapacity:0];
[str4 appendString:@"123-456-789-000"];
NSRange r1={0,3};
NSRange r2={4,3};
NSRange r3={8,3};
NSString*str5=[str4 substringWithRange:r1];
NSString*str6=[str4 substringWithRange:r2];
NSString*str7=[str4 substringWithRange:r3];
NSMutableString *str8=[NSMutableString stringWithCapacity:0];
[str8 appendString:@""];
[str8 appendString:str5];//添加字符串
[str8 appendString:str6];
[str8 appendString:str7];
NSLog(@"%@",str8);
//第二种方法
NSString *str5=@"123-456-789-000";
NSArray *newArray=[str5 componentsSeparatedByString:@"-"];//用什么分开
NSLog(@"%@",newArray);
NSMutableString *newStr=[NSMutableString stringWithCapacity:0];
for (NSString *s in newArray)// s是指向元素
{
[newStr appendString:s];
}
NSLog(@"newStr =%@",newStr);
//第三种方法
NSString *str5=@"123-456-789-000";
NSString *newStr5= [str5 stringByReplacingOccurrencesOfString:@"-" withString:@""];//替换法把-替换成空
NSLog(@"newStr5=%@",newStr5);
//4放四个十进制三位数到一个数组中，然后按从小到大排序后组成一个新的数组
NSMutableArray *numArray=[[NSMutableArray alloc]initWithObjects:@"114",@"159",@"210",@"999", nil];
for (int i=0; i<</span>numArray.count; i++)
{
for (int j=(i+1); j<</span>4; j++)
{
int a=[[numArray objectAtIndex:i] intValue]; //取值
int b=[[numArray objectAtIndex:i] intValue];
if (a>b)
{
[numArray exchangeObjectAtIndex:i withObjectAtIndex:j];
}
}
}
NSLog(@"numArray =%@",numArray);

第二种方法

NSMutableArray *numArray=[[NSMutableArray alloc]initWithObjects:@"114",@"159",@"210",@"999", nil];
for (int i=0; i<[numArray count]; i++)//冒泡法比较
{
for (int j=0; j<4-i; j++)
{
int a=[[numArray objectAtIndex:i] intValue]; //取值
int b=[[numArray objectAtIndex:i] intValue];
if (a>b)
{
[numArray exchangeObjectAtIndex:i withObjectAtIndex:j];
}
}
}
NSLog(@"numArray =%@",numArray);

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