XDU 1011

解法1:TLE

#include<stdio.h>
int main()
{
    long long n;
    //freopen("in.txt","r",stdin);
    while(scanf("%lld",&n)!=EOF){
        long long i=,s=;
        while(s<=n){
            s=i*i;
            i++;
        }
        if(i%!=)
            printf("odd\n");
        else
            printf("even\n");
    }
    return ;
}

解法2:AC

#include<bits/stdc++.h>
using namespace std;
#define maxn 1e10
long long sum(long long t)
{
    return t*(t+);
}
int main()
{
    long long n;
    //freopen("in.txt","r",stdin);
    while(scanf("%lld",&n)!=EOF)
    {
        long long r=maxn,l=,mid=(maxn+)/;
        while()
        {
            if(sum(mid)>n)
            {
                if(sum(mid-)==n){
                    mid--;
                    break;
                }
                if(sum(mid-)<n)
                    break;
                r=mid;
                mid=(l+r)/;
            }
            else{
                if(sum(mid+)>=n){
                    mid++;
                    break;
                }
                l=mid;
                mid=(l+r)/;
            }
        }
        if(mid%)
            printf("odd\n");
        else
            printf("even\n");
    }
}