C++实现真值表
这一片文章主要是关于真值表,在完成之前我也遇到了许多问题。比如怎么去求解表达式的值,怎么去将每个变量进行赋值,也就是如何 将n个字符进行01全排列。
01全排列真的神奇,01全排列其实就是2^n。他可以表示全部的01,真是神奇。
怎么去判断表达式的值呢?我们可以分步骤:
1.先去括号 即 ()/(a);
2.去非 !;
3.去&和|,经证明,他们两个的先后顺序不影响表达式的值;
4.去蕴含 -> 根据其含义进行判断就行;
5.最后就是去等价了 <-> ,同上。
#include<bits/stdc++.h>
using namespace std;
string s, tmp; //表达式
int cnt; //变量个数
char st[26];//统计字母,全部小写字母表示
int f[26];//统计每个变量的赋值情况
int f_t, f_f;//判断表达式的类别
void input(); //界面提示
void Vs(string s, char *c);//变量统计
void output();//输出变量符合和表达式
string vSubstitution();//变量替换
string rBrackets(); //去括号 包括()/(p)
string gToAfrica();//去非
string tJoin();//去析取
string tDisjunct();//去合取
string tContain();//去蕴含
string dEquivalent();//去等价
int main() {
input();
cin >> s;
puts("");
puts("");
cout << s << ' ';
puts("的真值表如下:");
puts("");
tmp = s;
Vs(s, st);
output();
int n;//不同赋值的方法数
n = pow(2, cnt);
cout << '|';
for (int i = 0; i < cnt; i++) cout << "---";
for (int i = 1; i <= tmp.length(); i ++) cout << '-';
cout << '|';
puts("");
for (int i = 0; i < n; i ++) {
cout << '|';
for (int j = 0; j < cnt; j ++) { //赋值过程
f[st[j] - 'a'] = (1 & (i >> (cnt - 1 - j)));
}
for (int j = 0; j < cnt; ++j) {
cout << f[st[j] - 'a'] << " |";
}
for (int i = 0; i < tmp.length() / 2; i ++) cout << ' ';
s = vSubstitution();
while (s.length() > 1) { //循环判断
s = rBrackets();
s = gToAfrica();
s = tJoin();
s = tDisjunct();
s = tContain();
s = dEquivalent();
}
cout << s;
if (!(tmp.length() % 2)) {
for (int i = 1; i < tmp.length() / 2; i ++) cout << ' ';
cout << '|';
} else if (tmp.length() == 1) cout << "|";
else {
for (int i = 1; i < tmp.length() / 2; i ++) cout << ' ';
cout << " |";
}
puts("");
if(s=="0") f_f++;
else f_t++;
s = tmp;
}
cout << '|';
for (int i = 0; i < cnt; i++) cout << "---";
for (int i = 1; i <= tmp.length(); i ++) cout << '-';
cout << '|';
puts("");
cout << tmp << " 的类型是:";
if(f_f==n) puts("矛盾式");
else if(f_t==n) puts("重言式");
else puts("可满足式");
return 0;
}
void input() {
puts("表达式规则如下:");
puts("否定连接词:!");
puts("合取连接词:|");
puts("析取连接词:&");
puts("蕴含连接词:->");
puts("等价连接词:<->");
puts("请按规范输入表达式,字符间请不要有空格!否则将会程序无法正常运行。");
puts("----------------------------------------------------------------------------------------------------------------------");
puts("请输入你的表达式:") ;
}
void Vs(string s, char *c) {
int ch[26] = {};
for (int i = 0; i < s.length(); i ++) {
if (isalpha(s[i])) ch[s[i] - 'a']++; //isalpha判断字符是否为小写字母
}
for (int i = 0; i < 26; i ++) {
if (ch[i]) st[cnt++] = i + 97;
}
}
void output() {
cout << '|';
for (int i = 0; i < cnt; i++) cout << "---";
for (int i = 1; i <= tmp.length(); i ++) cout << '-';
cout << '|';
puts("");
cout << '|';
for (int i = 0; i < cnt; i ++) {
cout << st[i] << " |";
}
cout << s << '|' << endl;
}
string vSubstitution() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if (s[i] <= 'z' && s[i] >= 'a') {
ss += f[s[i] - 'a'] ? "1" : "0";
} else ss += s[i];
}
return ss;
}
string rBrackets() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if (s[i] == '(' && (i + 2) < s.length() && s[i + 2] == ')') ss += s[i + 1], i += 2;
else ss += s[i];
}
return ss;
}
string gToAfrica() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if (s[i] == '!' && (i + 1) < s.length() && s[i + 1] == '0') ss += '1', i ++;
else if (s[i] == '!' && (i + 1) < s.length() && s[i + 1] == '1') ss += '0', i ++;
else ss += s[i];
}
return ss;
}
string tJoin() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if ((s[i] == '0' && (i + 2) < s.length() && s[i + 2] == '1' && s[i + 1] == '|') || (s[i] == '1' && (i + 2) < s.length() && s[i + 2] == '0' && s[i + 1] == '|') || (s[i] == '1' && (i + 2) < s.length() && s[i + 2] == '1' && s[i + 1] == '|')) ss += '1', i += 2;
else if ((s[i] == '0' && (i + 2) < s.length() && s[i + 2] == '0' && s[i + 1] == '|')) ss += '0', i += 2;
else ss += s[i];
}
return ss;
}
string tDisjunct() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if ((s[i] == '0' && (i + 2) < s.length() && s[i + 2] == '1' && s[i + 1] == '&') || (s[i] == '0' && (i + 2) < s.length() && s[i + 2] == '0' && s[i + 1] == '&') || (s[i] == '1' && (i + 2) < s.length() && s[i + 2] == '0' && s[i + 1] == '&')) ss += '0', i += 2;
else if ((s[i] == '1' && (i + 2) < s.length() && s[i + 2] == '1' && s[i + 1] == '&')) ss += '1', i += 2;
else ss += s[i];
}
return ss;
}
string tContain() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if (s[i] == '1' && (i + 3) < s.length() && s[i + 3] == '0' && s[i + 1] == '-' && s[i + 2] == '>') ss += '0', i += 3;
else if ((s[i] == '1' && (i + 3) < s.length() && s[i + 3] == '1' && s[i + 1] == '-' && s[i + 2] == '>') || (s[i] == '0') && (i + 3) < s.length() && s[i + 1] == '-' && s[i + 2] == '>' && (s[i + 3] == '0' || s[i + 3] == '1') ) ss += '1', i += 3;
else ss += s[i];
}
return ss;
}
string dEquivalent() {
string ss = "";
for (int i = 0; i < s.length(); i ++) {
if ((s[i] == '0' && (i + 4) < s.length() && s[i + 4] == '0' && s[i + 1] == '<' && s[i + 2] == '-' && s[i + 3] == '>') || (s[i] == '1' && (i + 4) < s.length() && s[i + 4] == '1' && s[i + 1] == '<' && s[i + 2] == '-' && s[i + 3] == '>') ) ss += '1', i += 4;
else if ((s[i] == '1' && (i + 4) < s.length() && s[i + 4] == '0' && s[i + 1] == '<' && s[i + 2] == '-' && s[i + 3] == '>') || (s[i] == '0' && (i + 4) < s.length() && s[i + 4] == '1' && s[i + 1] == '<' && s[i + 2] == '-' && s[i + 3] == '>') ) ss += '0', i += 4;
else ss += s[i];
}
return ss;
}
没有什么能阻止我对知识的追求!!!