评估表示为字符串的布尔表达式
给定一个仅由 0、1、A、B、C 组成的字符串,其中
A = 与
B = 或
C = 异或
假设没有优先顺序并且从左到右进行评估,则计算字符串的值。
约束——字符串的长度是奇数。它总是一个有效的字符串。
例如,1AA0 不会作为输入给出。
例子:
Input : 1A0B1
Output : 1
1 AND 0 OR 1 = 1
Input : 1C1B1B0A0
Output : 0
资料来源:2017 年微软在线实习轮
这个想法是通过在每次迭代后跳转一个字符来遍历所有操作数。对于当前操作数str[i],检查str[i+1]和str[i+2]的值,据此决定当前子表达式的值。
C++
// C++ program to evaluate value of an expression.
#include
using namespace std;
int evaluateBoolExpr(string s)
{
int n = s.length();
// Traverse all operands by jumping
// a character after every iteration.
for (int i = 0; i < n; i += 2) {
// If operator next to current operand
// is AND.
if (s[i + 1] == 'A') {
if (s[i + 2] == '0'|| s[i] == '0')
s[i + 2] = '0';
else
s[i + 2] = '1';
}
// If operator next to current operand
// is OR.
else if (s[i + 1] == 'B') {
if (s[i + 2] == '1'|| s[i] == '1')
s[i + 2] = '1';
else
s[i + 2] = '0';
}
// If operator next to current operand
// is XOR (Assuming a valid input)
else {
if (s[i + 2] == s[i])
s[i + 2] = '0';
else
s[i + 2] = '1';
}
}
return s[n - 1] -'0';
}
// Driver code
int main()
{
string s = "1C1B1B0A0";
cout << evaluateBoolExpr(s);
return 0;
}
Java
// Java program to evaluate value of an expression.
public class Evaluate_BoolExp {
// Evaluates boolean expression
// and returns the result
static int evaluateBoolExpr(StringBuffer s)
{
int n = s.length();
// Traverse all operands by jumping
// a character after every iteration.
for (int i = 0; i < n; i += 2) {
// If operator next to current operand
// is AND.
if( i + 1 < n && i + 2 < n)
{
if (s.charAt(i + 1) == 'A') {
if (s.charAt(i + 2) == '0' ||
s.charAt(i) == 0)
s.setCharAt(i + 2, '0');
else
s.setCharAt(i + 2, '1');
}
// If operator next to current operand
// is OR.
else if ((i + 1) < n &&
s.charAt(i + 1 ) == 'B') {
if (s.charAt(i + 2) == '1' ||
s.charAt(i) == '1')
s.setCharAt(i + 2, '1');
else
s.setCharAt(i + 2, '0');
}
// If operator next to current operand
// is XOR (Assuming a valid input)
else {
if (s.charAt(i + 2) == s.charAt(i))
s.setCharAt(i + 2, '0');
else
s.setCharAt(i + 2 ,'1');
}
}
}
return s.charAt(n - 1) - '0';
}
// Driver code
public static void main(String[] args)
{
String s = "1C1B1B0A0";
StringBuffer sb = new StringBuffer(s);
System.out.println(evaluateBoolExpr(sb));
}
}
// This code is contributed by Sumit Ghosh
Python3
# Python3 program to evaluate value
# of an expression.
import math as mt
def evaluateBoolExpr(s):
n = len(s)
# Traverse all operands by jumping
# a character after every iteration.
for i in range(0, n - 2, 2):
# If operator next to current
# operand is AND.'''
if (s[i + 1] == "A"):
if (s[i + 2] == "0" or s[i] == "0"):
s[i + 2] = "0"
else:
s[i + 2] = "1"
# If operator next to current
# operand is OR.
else if (s[i + 1] == "B"):
if (s[i + 2] == "1" or s[i] == "1"):
s[i + 2] = "1"
else:
s[i + 2] = "0"
# If operator next to current operand
# is XOR (Assuming a valid input)
else:
if (s[i + 2] == s[i]):
s[i + 2] = "0"
else:
s[i + 2] = "1"
return ord(s[n - 1]) - ord("0")
# Driver code
s = "1C1B1B0A0"
string=[s[i] for i in range(len(s))]
print(evaluateBoolExpr(string))
# This code is contributed
# by mohit kumar 29
C#
// C# program to evaluate value
// of an expression.
using System;
using System.Text;
class GFG
{
// Evaluates boolean expression
// and returns the result
public static int evaluateBoolExpr(StringBuilder s)
{
int n = s.Length;
// Traverse all operands by jumping
// a character after every iteration.
for (int i = 0; i < n; i += 2)
{
// If operator next to current
// operand is AND.
if (i + 1 < n && i + 2 < n)
{
if (s[i + 1] == 'A')
{
if (s[i + 2] == '0' || s[i] == 0)
{
s[i + 2] = '0';
}
else
{
s[i + 2] = '1';
}
}
// If operator next to current
// operand is OR.
else if ((i + 1) < n && s[i + 1] == 'B')
{
if (s[i + 2] == '1' || s[i] == '1')
{
s[i + 2] = '1';
}
else
{
s[i + 2] = '0';
}
}
// If operator next to current operand
// is XOR (Assuming a valid input)
else
{
if (s[i + 2] == s[i])
{
s[i + 2] = '0';
}
else
{
s[i + 2] = '1';
}
}
}
}
return s[n - 1] - '0';
}
// Driver code
public static void Main(string[] args)
{
string s = "1C1B1B0A0";
StringBuilder sb = new StringBuilder(s);
Console.WriteLine(evaluateBoolExpr(sb));
}
}
// This code is contributed by Shrikant13
PHP
Javascript
输出:
0