leetcode 413. Arithmetic Slices

原题：

A sequence of number is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.

For example, these are arithmetic sequence:

1, 3, 5, 7, 97, 7, 7, 73, -1, -5, -9

The following sequence is not arithmetic.

1, 1, 2, 5, 7

A zero-indexed array A consisting of N numbers is given. A slice of that array is any pair of integers (P, Q) such that 0 <= P < Q < N.

A slice (P, Q) of array A is called arithmetic if the sequence:
A[P], A[p + 1], ..., A[Q - 1], A[Q] is arithmetic. In particular, this means that P + 1 < Q.

The function should return the number of arithmetic slices in the array A.

找出等差数列组里面，所有等差数列。

代码如下：

int numberOfArithmeticSlices(int* A, int ASize) {    int result=0;    int* count;    count=(int*)malloc(sizeof(int)*ASize);    //resize the A list to make a signal.    int *B;    B=(int*)malloc(sizeof(int)*(ASize+1));    for(int n=0;n<ASize;n++)    {        *(B+n)=*(A+n);    }    *(B+ASize)=INT_MIN;    int flag_count=0;    int flag_serial=1;    int k;    for(int n=1;n<ASize;n++)    {        if(flag_serial==1)        {            n--;            k=*(B+n)-*(B+n+1);        }        if(*(B+n)==(*(B+n+1)+k))        {            flag_serial++;        }        else        {            if(flag_serial>=3)            {                *(count+flag_count)+=flag_serial;                flag_count+=1;            }            flag_serial=1;        }        //printf("%d",n);    }    //printf("%d",flag_count);    for(int n=0;n<flag_count;n++)    {        for(int m=1;m<=*(count+n)-2;m++)        {            result+=m;        }    }    return result;}

在最后一组解的时候，出现了这种情况。

这种情况有没有大佬给解释一下。。。

说下思路

基本上就是一个基本遍历，另外找规律的过程。

不是很难。