1106. Parsing A Boolean Expression
Return the result of evaluating a given boolean expression, represented as a string.
An expression can either be:
- “t”, evaluating to True;
- “f”, evaluating to False;
- “!(expr)”, evaluating to the logical NOT of the inner expression expr;
- “&(expr1,expr2,…)”, evaluating to the logical AND of 2 or more inner expressions expr1, expr2, …;
- “|(expr1,expr2,…)”, evaluating to the logical OR of 2 or more inner expressions expr1, expr2, …
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| class Solution {
bool evalAnd(string& exp, int& p) {
p += 2;
auto res = true;
res &= eval(exp, p);
while(exp[p] != ')') {
p++;
res &= eval(exp, p);
}
p++;
return res;
}
bool evalOr(string& exp, int& p) {
p += 2;
auto res = false;
res |= eval(exp, p);
while(exp[p] != ')') {
p++;
res |= eval(exp, p);
}
p++;
return res;
}
bool evalNot(string& exp, int& p) {
p += 2;
auto res = eval(exp, p);
p++;
return !res;
}
bool eval(string& exp, int& p) {
if(exp[p] == 't') {
p++;
return true;
} else if(exp[p] == 'f') {
p++;
return false;
} else if(exp[p] == '&') {
return evalAnd(exp, p);
} else if(exp[p] == '|') {
return evalOr(exp, p);
} else return evalNot(exp, p);
}
public:
bool parseBoolExpr(string expression) {
int pos = 0;
return eval(expression, pos);
}
};
|
