移除array中重复的item

//move the repeated item
            NSInteger index = [orignalArray count] - 1;
            for (id object in [orignalArray reverseObjectEnumerator]) {
                if ([orignalArray indexOfObject:object inRange:NSMakeRange(0, index)] != NSNotFound) {
                    [orignalArray removeObjectAtIndex:index];
                }
                index--;
            }