UVA 12716

【题目分析】
a^b>=a-b>=gcd(a,b)

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【代码】

#include <cstdio>#define ll long longll cnt[30000001];int tt,x,kase=0;int main(){    for (int i=1;i<=30000000;++i)        for (int j=i*2;j<=30000000;j+=i)            if ((j^i)==j-i) cnt[j]++;    for (int i=1;i<=30000000;++i)        cnt[i]+=cnt[i-1];    scanf("%d",&tt);    while (tt--)    {        scanf("%d",&x);        printf("Case %d: %lld\n",++kase,cnt[x]);    }}