面试题分享【不断更新】

问题1：求以下程序段的输出

int test(int x, int y)
{
    x = x + y;
    return x * y;
}

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        int x = 3, y = 10, z = test(x, y);
        NSLog(@"%d%d", x++, ++z);
    }
    return 0;
}

答案：3131问题2：求以下程序段的输出

int func(int x)
{
    int countx = 0;
    while (x) {
        countx++;
        x = x&(x-1);
    }
    return countx;
}

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        
        NSLog(@"%d", func(2013));
    }
    return 0;
}

答案：9 问题3：简述两个for循环的优缺点

for (i = 0; i < N; i++) {
    if (condition) {
        doSomeThing();
    } else {
        doOtherThing();
    }
}

if (condition) {
    for (i = 0; i < N; i++) {
        doSomeThing();
    }
} else {
    for (i = 0; i < N; i++) {
        doOtherThing();
    }
}

答案：无 问题4：请指出下面代码的问题

UIView *tmpView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.view addSubview:tmpView];

答案：无 问题5：你所了解的单例有哪些？请写了一个单例的示例代码。答案：

@interface Manager : NSObject
+ (id)sharedManager;
@end

static Manager *instance = nil;

@implementation Manager

+ (id)sharedManager
{
    if (!instance) {
        instance = [[super allocWithZone:NULL] init];
    }
    return instance;
}

// 复写allocWithZone和copyWithZone的目的是在外部多次调用alloc的时候，内部能够确保对象只创建了一次

+ (id)allocWithZone:(NSZone *)zone
{
    return [[self sharedManager] retain];
}

- (id)copyWithZone:(NSZone *)zone
{
    return self;
}

// 复写retain、retainCount、release、autorelease避免单件对象被外部释放
- (id)retain
{
    return self;
}

- (NSUInteger)retainCount
{
    return NSUIntegerMax;
}

- (void)release
{
    
}

- (id)autorelease
{
    return self;
}

问题6：在你的日常开发过程中，是否遇到过崩溃问题？怎么解决？答案：无问题7：请写出使用委托（代理）的示例代码。答案：A委托BA.h

@protocol ADelegate;
@interface A : NSObject

@property (nonatomic, assign) id<ADelegate> delegate;

- (void)go;

@end

@protocol ADelegate <NSObject>

- (void)doSomeThing;

@end

A.m

@implementation A

- (void)go
{
    if ([_delegate respondsToSelector:@selector(doSomeThing)]) {
        [_delegate doSomeThing];
    }
}

@end

B.h

#import "A.h"

@interface B : NSObject<ADelegate>

@end

B.m

@implementation B

- (void)doSomeThing
{
    NSLog(@"do something...");
}

@end

man.m

#import "A.h"
#import "B.h"

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        A *a = [[A alloc] init];
        B *b = [[B alloc] init];
        a.delegate = b;
        
        [a go];
        
        [a release];
        [b release];
        
    return 0;
    }
}

// 输出do something...问题8：写出控制器加载视图的常规调用方法流程。答案：loadViewviewDidLoadviewWillAppearviewWillLayoutSubviewsviewDidLayoutSubviewsviewDidAppear问题9：Objective-C有多重继承么？不是的话，请以示例代码说明。答案：无问题10：请写出下面代码的打印结果（默认在32位机器下运行）。

char a[] = "hello world";
char *p = a;
NSLog(@"%ld", sizeof(a));
NSLog(@"%ld", sizeof(p));

答案：124如果在64位机器上运行128问题11： 请完成下面的函数

@interface NSCustomArray : NSArray
@property (nonatomic, retain) NSArray *targets;
- (void)updateTargetsByArray:(NSArray *)newArray; // 将newArray赋值给targets
@end

@implementation NSCustomArray

- (void)updateTargetsByArray:(NSArray *)newArray
{
    NSArray *tmpArray = [[NSArray alloc] initWithArray:newArray];
    // 将tmpArray赋值给targets
}
@end

答案：无 问题12：检查如下代码是否有问题，如果有问题，正确的写法是？

- (void)setTarget:(NSObject *)target
{
    self.target = target;
}

答案：无 问题13：指出下面代码的问题

- (void)willEndStepOne:(NSObject *)userInfo
{
    [NSThread detachNewThreadSelector:@selector(doSomeThing:) toTarget:self withObject:userInfo];
}

- (void)doSomeThing:(NSObject *)userInfo
{
    int max_loop_times = 999999;
    for (int i=0; i<max_loop_times; i++) {
        int randNum = rand();
        NSString *tmpString = [NSString stringWithFormat:@"%d", randNum];
        NSLog(@"%@", tmpString);
    }
}

答案：无