CF Hello 2018 913E

题目大意:

多组数据,给你一张真值表,求字典序最小的表达式。(真值表只有3个变量x,y,z)

我们发现答案不会很长,而且我们只有 256 种不同的输入,那么我们就可以打表。

我们怎么打表呢?我们发现答案不会很长,那么我们搜索表达式至len为20位,再加上最优性剪枝。跑个3min就出来了。

(看起来有8^20 次方种,很多,其实很多是不符合语法的,符合语法的也有可以剪枝的,比如A&___,A已经flase,就不用做下去了)。

(不要加一位就判一次,可以搜索3位判一次剪枝。)

#include<bits/stdc++.h>
#define sight(c) ('0'<=c&&c<='9')
using namespace std;
int n,a;
inline void read(int &x,int t){
    static char c;
    for (c=getchar();!sight(c);c=getchar());
    for (x=0;sight(c);c=getchar()) x=x*t+c-48;
} 
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int main () {
//    freopen("a.in","r",stdin);
    read(n,10);
    while(n--) {
        read(a,2);
        printf("%s
",ch[a]);
    }
}
原文地址:https://www.cnblogs.com/rrsb/p/8268017.html