iphone - Objective-C for循环问题

Question

我有两个方法，在testMethod中调用了generateRandomCard方法，其中有一个for循环运行100次。这样，它可以完美工作，但是如果我将for循环限制设置为1000或任何其他大于100的数字，则会崩溃。你知道出什么事了吗？

- (void)testMethod {

    Globals *myGlobals = [Globals sharedInstance];
    int rankOfFirst = 0;
    int rankOfSecond = 0;
    int playerOneWin = 0;
    int playerTwoWin = 0;
    int ties = 0;
    float firstPercent = 0;
    float secondPercent = 0;
    float tiePercent = 0;
    FiveEval *evaluator = [FiveEval theEvaluator];

    for (int i = 0; i < 100; i++) {
        short fPF = [self generateRandomCard];
        short fPS = [self generateRandomCard];
        short sPF = [self generateRandomCard];
        short sPS = [self generateRandomCard];
        short fFlop = [self generateRandomCard];
        short sFlop = [self generateRandomCard];
        short tFlop = [self generateRandomCard];
        short tur = [self generateRandomCard];
        short riv = [self generateRandomCard];

        rankOfFirst = [evaluator getRankOfSeven:fFlop 
                                               :sFlop 
                                               :tFlop
                                               :tur 
                                               :riv 
                                               :fPF 
                                               :fPS];

        rankOfSecond = [evaluator getRankOfSeven:fFlop 
                                             :sFlop 
                                             :tFlop 
                                             :tur 
                                             :riv 
                                             :sPF 
                                             :sPS];

        if (rankOfFirst > rankOfSecond) {
            playerOneWin++;
        } else if (rankOfSecond > rankOfFirst) {
            playerTwoWin++;
        } else {
            ties++;
        }

        [myGlobals.alreadyPickedCards removeAllObjects];
    }

    firstPercent = ((float)playerOneWin/(float)10000)*100;
    secondPercent = ((float)playerTwoWin/(float)10000)*100;
    tiePercent = ((float)ties/(float)10000)*100;

    NSLog(@"First Player Equity: %f", firstPercent);
    NSLog(@"Second Player Equity: %f", secondPercent);
    NSLog(@"Tie Equity: %f", tiePercent);
}


- (short)generateRandomCard {

    Globals *myGlobals = [Globals sharedInstance];
    short i = arc4random()%51;
    for (int j = 0; j < [myGlobals.alreadyPickedCards count]; j++) {
        if (i == [[myGlobals.alreadyPickedCards objectAtIndex:j] shortValue]) {
            [self generateRandomCard];
        }
    }
    [myGlobals.alreadyPickedCards addObject:[NSNumber numberWithShort:i]];
    return i;
}

Answer 1

您可能在-generateRandomCard的递归调用中是overflowing your stack。如果生成的卡片已经被拾取，则将递归调用自己(并忽略结果，这是一个不同的错误)。因此，如果您的随机数流给您带来了不幸的序列，该序列使您已经选择的返还牌一直保留下来，那么您将无限递归直到筹码量溢出。

更改卡选择算法，以便与其使用可能无限循环/递归的rejection sampling，不如使用带有有限运行时间的算法Fisher-Yates shuffle。