The codes in addSpriteWithoutQuad from cocos2d-iphone is:

-(id) addSpriteWithoutQuad:(CCSprite*)child z:(NSUInteger)z name:(NSString*)name
{
... 
    // XXX: optimize with a binary search
    int i=0;
    for( CCSprite *c in _descendants ) {
        if( c.atlasIndex >= z )    // Here we check if index is larger than z, break, so the element's atlastIndex in _descendants is from high value to low value.
            break;
        i++;
    }
    [_descendants insertObject:child atIndex:i];
...
}
@end

BUT IN COCOS2D-X, THE LOGIC WAS TOTALLY DIFFERENT.¶

CCSpriteBatchNode * CCSpriteBatchNode::addSpriteWithoutQuad(CCSprite*child, unsigned int z, int aTag)
{
...
    // XXX: optimize with a binary search
    int i=0;

    CCObject* pObject = NULL;
    CCARRAY_FOREACH(m_pobDescendants, pObject)
    {
    CCARRAY_FOREACH(m_pobDescendants, pObject)
    {
        CCSprite* pChild = (CCSprite*) pObject;
        if (pChild && (pChild->getAtlasIndex() >= z))   // Wrong logic here.........shit
        {
            ++i;
        }
    }
...
}

OUCH.