二维数组找最大值

int Search(int* arr,int x,int y,int num)
{
　 //把二维数组当做一维数组处理
    if(arr == NULL || x <= 0 || y<= 0) return -1;
    int a = x-1;
    int b = 0;
    while(a >= 0 && a < x && b >=0 && b < y)
    {
        if(arr[a*y+b] > num)
        {
            a--;
        }
        else if(arr[a*y+b] < num)
        {
            b++;
        }
        else
            return 1;
    }
    return -1;
}

int main()
{
    int arr[5][5] = {1,55,79,82,88,
                     2,56,80,83,109,
                     3,57,81,84,110,
                     4,58,90,100,120,
                     5,59,99,111,122};

    int index = 0;
    index = Search((int*)arr,5,5,89);
    printf("%d",index);
    return 0;
}