假设NavigationController有ABC三个ViewController,A push B,B push C 要求C返回的时候直接返回A，即移除B（popToRoot不予考虑，A之前可能还有其他的）
解决方案：修改viewControllers数组
NSMutableArray* navArray = [[NSMutableArray alloc] initWithArray:self.navigationController.viewControllers];
[navArray replaceObjectAtIndex:[navArray count]-1 withObject:nextViewController]; [self.navigationController setViewControllers:navArray animated:YES];
