标签:putchar define gif ORC etc for 多少 closed lan
小希称只含7和8的数是幸运数,那么不超过n位的幸运数有多少个?
Input
一个整数 n (1 ≤ n ≤ 55)
Output
输出幸运数的数量
Example
Input
2
Output
6
sol:这和0,1有个屁区别 ----摘自yj大佬原话
结论非常显然小学生都知道 2n+1-2
#include <bits/stdc++.h> using namespace std; typedef long long ll; inline ll read() { ll s=0; bool f=0; char ch=‘ ‘; while(!isdigit(ch)) { f|=(ch==‘-‘); ch=getchar(); } while(isdigit(ch)) { s=(s<<3)+(s<<1)+(ch^48); ch=getchar(); } return (f)?(-s):(s); } #define R(x) x=read() inline void write(ll x) { if(x<0) { putchar(‘-‘); x=-x; } if(x<10) { putchar(x+‘0‘); return; } write(x/10); putchar((x%10)+‘0‘); return; } #define W(x) write(x),putchar(‘ ‘) #define Wl(x) write(x),putchar(‘\n‘) ll n; int main() { ll ans=0; R(n); Wl(1ll*((1ll<<(n+1))-2)); return 0; }
标签:putchar define gif ORC etc for 多少 closed lan
原文地址:https://www.cnblogs.com/gaojunonly1/p/10651230.html