1.棧里存在

for (UIViewController *vc in [self.navigationController viewControllers]) {
        if ([vc isKindOfClass:[MonthlyExamDetailController class]]) {
            [self.navigationController popToViewController:vc animated:YES];
        }
}

2.棧里不存在

NSMutableArray*tempMarr =[NSMutableArray arrayWithArray:self.navigationController.viewControllers];
MonthlyExamDetailController *vc = [self.storyboard instantiateViewControllerWithIdentifier:NSStringFromClass([MonthlyExamDetailController class])];
[tempMarr insertObject:vc atIndex:tempMarr.count- 1];
[self.navigationController setViewControllers:tempMarr animated:YES];
for (UIViewController *vc in [self.navigationController viewControllers]) {
            if ([vc isKindOfClass:[MonthlyExamDetailController class]]) {
                   [self.navigationController popToViewController:vc animated:YES];
            }
}