面試題分享【不斷更新】

問題1：求以下程序段的輸出

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

---

問題2：求以下程序段的輸出

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

---

 

問題3：簡述兩個for循環的優缺點

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：無

---

 

問題4：請指出下面代碼的問題

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

答案：無

---

 

問題5：你所了解的單例有哪些？請寫了一個單例的示例代碼。

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;
}

// 復寫allocWithZone和copyWithZone的目的是在外部多次調用alloc的時候，內部能夠確保對象只創建了一次

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

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

// 復寫retain、retainCount、release、autorelease避免單件對象被外部釋放
- (id)retain
{
    return self;
}

- (NSUInteger)retainCount
{
    return NSUIntegerMax;
}

- (void)release
{
    
}

- (id)autorelease
{
    return self;
}

 

---

問題6：在你的日常開發過程中，是否遇到過崩潰問題？怎么解決？

答案：無

---

問題7：請寫出使用委托（代理）的示例代碼。

答案：

A委托B

A.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;
    }
}

// 輸出

do something...

---

問題8：寫出控制器加載視圖的常規調用方法流程。

答案：

loadView

viewDidLoad

viewWillAppear

viewWillLayoutSubviews

viewDidLayoutSubviews

viewDidAppear

---

問題9：Objective-C有多重繼承么？不是的話，請以示例代碼說明。

答案：無

---

問題10：請寫出下面代碼的打印結果（默認在32位機器下運行）。

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

答案：

12

4

如果在64位機器上運行

12

8

---

問題11： 請完成下面的函數

@interface NSCustomArray : NSArray
@property (nonatomic, retain) NSArray *targets;
- (void)updateTargetsByArray:(NSArray *)newArray; // 將newArray賦值給targets
@end

@implementation NSCustomArray

- (void)updateTargetsByArray:(NSArray *)newArray
{
    NSArray *tmpArray = [[NSArray alloc] initWithArray:newArray];
    // 將tmpArray賦值給targets
}
@end

答案：無

---

 

問題12：檢查如下代碼是否有問題，如果有問題，正確的寫法是？

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

答案：無

---

 

問題13：指出下面代碼的問題

- (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：無