在相邻元素相差1的数组中查找某一特定元素第一次出现的位置

题目：数组中相邻的每两个数之间的差值是1或-1，给定一个数N，求如何找到第一个N的位置。

如：3,4,3,2,1,2,3,4,3,4,5,6,5   求第一个5所在的位置。

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    int a[] = {3,4,3,2,1,2,3,4,3,4,5,6,5};
    int i, next, to_search;
    int len = sizeof(a);
    int count = 0, found = 0;

    printf("Please input the number that you want to search: ");
    scanf("%d",&to_search);

    for( i=0; i<len; i+=next)
    {
        ++count;
        if( a[i] == to_search )
        {
            found = 1;
            break;
        }
        else
            next = abs(a[i]-to_search);
    }
    printf("Search times: %d\n",count);
    if( found )
        printf("%d is at a[%d]\n",to_search, i);
    else
        printf("Not found.\n");

    return 0;
}