codeforce 11B 思维题

http://codeforces.com/problemset/problem/11/B

B. Jumping Jack

time limit per test

1 second

memory limit per test

64 megabytes

input

standard input

output

standard output

Jack is working on his jumping skills recently. Currently he's located at point zero of the number line. He would like to get to the point x. In order to train, he has decided that he'll first jump by only one unit, and each subsequent jump will be exactly one longer than the previous one. He can go either left or right with each jump. He wonders how many jumps he needs to reach x.

Input

The input data consists of only one integer x ( - 109 ≤ x ≤ 109).

Output

Output the minimal number of jumps that Jack requires to reach x.

Sample test(s)

input

2

output

3

input

6

output

3

input

0

output

0

解题思路：假设所有的步数都是向右走的，那么当步数n走完后，（（n+1）*n）/2>x时，如果（（n+1）*n）/2-x==t是偶数的话，那么我们第t/2步设为往左走即可，步数不变。那么现在如果t 为奇数就先不做处理，继续向右走，直到凑出偶数为止，结果显而易见了。

#include <iostream>#include<cstdio>using namespace std;int main(){    int x,n,s,w;    while(~scanf("%d",&x))    {        n=0;        x=x>=0?x:-x;        while(1)        {            s=n*(n+1)/2;            if(x==s)                break;            if(s>x)            {                int c=s-x;                if(c%2==0)                    break;            }            n++;        }        cout<<n<<endl;    }    return 0;}