在特定规律的数组中查找某元素

给定数组A[n]，其中 A[i+1] = A[i]+1 OR A[i]-1,和数字k，请用最有效的方式在数组A中查找k。

Given an array A[n] such that A[i+1] = A[i]+1 OR A[i]-1, and a number k, can you determine in most efficient way whether k is present in A[n] or not?

对A[0],如果它不等于k，求出他和k相差的绝对值diff，考查0+diff处的值。如果不等于k，重复以上步骤。直到找到k，或者遍历完数组。

bool Find_elem(int a[],int length,int expectedNum){int i = 0;while (i < length){if (a[i] == expectedNum){return true;}else{int diff = abs(expectedNum - a[i]);i = i+diff;}}return false;}