如何找到第三小的整数

我有一个未知大小的数组，想在不排序的情况下找到第三小的整数，我该怎么做？

这是我的尝试，但我没能成功。

int getThirdSmallest(int* arr, int size) {
    int first = arr[0];
    int second = 0;
    int third = 0;
    for (int i = 0; i > size; i++) {
        if (first > arr[i]) {
            third = second;
            second = first;
            first = arr[i];
        } else if (second > arr[i]) {
            third = second;
            second = arr[i];
        }
        else if (third > arr[i]) {
            third = arr[i];
        }
    }
    return third;
}