去除数组中相同的元素

如题，上代码

- (void)removeTheSameElementsFromTheArray{
    NSMutableArray *sortArray = [NSMutableArray array];
    NSMutableArray *arrayA = [NSMutableArray arrayWithArray:@[@(3), @(2), @(5), @(2), @(5), @(4), @(3)]];
    while (arrayA.count > 0) {
        [sortArray addObject:arrayA.firstObject];
        NSInteger first = [[NSString stringWithFormat:@"%@", arrayA.firstObject] integerValue];
        [arrayA removeObjectAtIndex:0];
        for (int i = 0; i < arrayA.count; ) {
            NSInteger second = [[NSString stringWithFormat:@"%@", arrayA[i]] integerValue];
            if (first == second) {
                [arrayA removeObjectAtIndex:i];
            }else{
                i ++;
            }
        }
    }
    NSLog(@"%@", sortArray);
}