给出二元变量 p,q,r,s,t以及运算符K,A,N,E,C,求所给运算符和变量的集合是否符合永真,若永真输出tautology,否则输出not。
思路: 首先构造出p,q,r,s,t可能的组合,因为只有5个变量,所以总共有2^5种状态,对这些状态逐一测试,看是否存在表达式为false的情况。采用dfs来递归地计算表达式。比如当遇到A时,它为二元,所以先递归计算第一个变量,它返回后正好是第二个变量。这种情况是唯一的,所以可以采用tot来统一计数。具体看代码:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Map;
import java.util.StringTokenizer;
public class Main{
String INPUT = "./data/judge/201712/P3295.txt";
public static void main(String[] args) throws IOException {
new Main().run();
}
int tot = 0;
boolean dfs(char[] cs, int p, int q, int r, int s, int t) {
char c = cs[tot++];
switch (c) {
case 'K':
boolean a = dfs(cs, p, q, r, s, t);
boolean b = dfs(cs, p, q, r, s, t);
if (a && b) return true;
return false;
case 'A':
a = dfs(cs, p, q, r, s, t);
b = dfs(cs, p, q, r, s, t);
if (!a && !b) return false;
else return true;
case 'N':
boolean not = dfs(cs, p, q, r, s, t);
return !not;
case 'C':
a = dfs(cs, p, q, r, s, t);
b = dfs(cs, p, q, r, s, t);
if (a && !b) return false;
else return true;
case 'E':
a = dfs(cs, p, q, r, s, t);
b = dfs(cs, p, q, r, s, t);
if (a && b || !a && !b) return true;
return false;
case 'p':
return p == 1;
case 'q':
return q == 1;
case 'r':
return r == 1;
case 's':
return s == 1;
case 't':
return t == 1;
}
return true;
}
void read() {
while (true) {
String data = ns();
if (data.equals("0")) break;
boolean judge = true;
for (int p = 0; p < 2 && judge; ++p) {
for (int q = 0; q < 2 && judge; ++q) {
for (int r = 0; r < 2 && judge; ++r) {
for (int s = 0; s < 2 && judge; ++s) {
for (int t = 0; t < 2 && judge; ++t) {
tot = 0;
if (!dfs(data.toCharArray(), p, q, r, s, t)) {
judge = false;
break;
}
}
}
}
}
}
if (judge) out.println("tautology");
else out.println("not");
}
}
FastScanner in;
PrintWriter out;
void run() throws IOException {
boolean oj;
try {
oj = ! System.getProperty("user.dir").equals("F:\\oxygen_workspace\\Algorithm");
} catch (Exception e) {
oj = System.getProperty("ONLINE_JUDGE") != null;
}
InputStream is = oj ? System.in : new FileInputStream(new File(INPUT));
in = new FastScanner(is);
out = new PrintWriter(System.out);
long s = System.currentTimeMillis();
read();
out.flush();
if (!oj){
System.out.println("[" + (System.currentTimeMillis() - s) + "ms]");
}
}
public boolean more(){
return in.hasNext();
}
public int ni(){
return in.nextInt();
}
public long nl(){
return in.nextLong();
}
public double nd(){
return in.nextDouble();
}
public String ns(){
return in.nextString();
}
public char nc(){
return in.nextChar();
}
class FastScanner {
BufferedReader br;
StringTokenizer st;
boolean hasNext;
public FastScanner(InputStream is) throws IOException {
br = new BufferedReader(new InputStreamReader(is));
hasNext = true;
}
public String nextToken() {
while (st == null || !st.hasMoreTokens()) {
try {
st = new StringTokenizer(br.readLine());
} catch (Exception e) {
hasNext = false;
return "##";
}
}
return st.nextToken();
}
String next = null;
public boolean hasNext(){
next = nextToken();
return hasNext;
}
public int nextInt() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Integer.parseInt(more);
}
public long nextLong() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Long.parseLong(more);
}
public double nextDouble() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Double.parseDouble(more);
}
public String nextString(){
if (next == null){
hasNext();
}
String more = next;
next = null;
return more;
}
public char nextChar(){
if (next == null){
hasNext();
}
String more = next;
next = null;
return more.charAt(0);
}
}
static class D{
public static void pp(int[][] board, int row, int col) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
sb.append(board[i][j] + (j + 1 == col ? "\n" : " "));
}
}
System.out.println(sb.toString());
}
public static void pp(char[][] board, int row, int col) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
sb.append(board[i][j] + (j + 1 == col ? "\n" : " "));
}
}
System.out.println(sb.toString());
}
}
static class ArrayUtils {
public static void fill(int[][] f, int value) {
for (int i = 0; i < f.length; ++i) {
Arrays.fill(f[i], value);
}
}
public static void fill(int[][][] f, int value) {
for (int i = 0; i < f.length; ++i) {
fill(f[i], value);
}
}
public static void fill(int[][][][] f, int value) {
for (int i = 0; i < f.length; ++i) {
fill(f[i], value);
}
}
}
static class Num{
public static <K> void inc(Map<K, Integer> mem, K k) {
if (!mem.containsKey(k)) mem.put(k, 0);
mem.put(k, mem.get(k) + 1);
}
}
}