WOJ1265-Recaman's Sequence

The Recaman's sequence is defined by a₀ = 0 ; for m > 0, a_m = a_m−1 − m if the rsulting a_m is positive and not already in the sequence, otherwise a_m = a_m−1 + m.
The first few numbers in the Recaman's Sequence is 0, 1, 3, 6, 2, 7, 13, 20, 12, 21, 11, 22, 10, 23, 9 ...
Given k, your task is to calculate ak.

 

输入格式

The input consists of several test cases. Each line of the input contains an integer k where 0 <= k <= 500000.
The last line contains an integer −1, which should not be processed.

输出格式

For each k given in the input, print one line containing ak to the output.

样例输入

710000-1

样例输出

2018658

//C++98#include <iostream>#include <cstdio>#include <map>using namespace std;long s[500005];map<long ,bool>hash;int main(){    int p;    long i,t;    s[0] = 0;    hash.clear();    hash[0]=1;    for(i=1; i<500003; i++){        t = s[i-1]-i;        if(t<=0 || hash[t])            s[i] = s[i-1]+i;        else            s[i] = t;        hash[s[i]] = true;    }    while(cin>>p && p!=-1)        cout<<s[p]<<endl;    return 0;}