CodeForces - 244B（dfs+剪枝，set）
题目链接题意：求小于n且最多由2个数组成的数的个数#include<bits/stdc++.h>using namespace std;set<long long>a;int n, x, y;void dfs(long long num, long long pos) { if (num > n || pos > 10)return; a.insert(num); dfs(num * 10 + x, pos +
