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| int NextPos(string& str, int pos){
int pos1 = str.find('+', pos + 1);
int pos2 = str.find('-', pos + 1);
if(pos1 != string::npos && pos2 != string::npos)
return min(pos1, pos2);
else if(pos1 != string::npos)
return pos1;
else if(pos2 != string::npos)
return pos2;
else
return string::npos;
}
class Solution {
public:
string solveEquation(string equation) {
if(equation[0] != '-')
equation = '+' + equation;
int pos = equation.find('=');
if(equation[pos + 1] != '-'){
equation = equation.substr(0, pos + 1) + '+'
+ equation.substr(pos + 1, equation.length() - pos - 1);
}
int countx = 0;
int sum = 0;
pos = equation.find('=');
int i = 0;
while(i < pos){
int nextpos = NextPos(equation, i);
if(nextpos > pos || nextpos == string::npos)
nextpos = pos;
if(equation[nextpos - 1] == 'x'){
string temp = equation.substr(i, nextpos - i - 1);
if(temp == "+")
countx++;
if(temp == "-")
countx--;
else{
if(temp[0] == '+')
countx += atoi(temp.substr(1, temp.length() - 1).c_str());
else
countx -= atoi(temp.substr(1, temp.length() - 1).c_str());
}
}
else{
string temp = equation.substr(i, nextpos - i);
if(temp[0] == '+')
sum -= atoi(temp.substr(1, temp.length() - 1).c_str());
else
sum += atoi(temp.substr(1, temp.length() - 1).c_str());
}
i = nextpos;
}
i = pos + 1;
while(i < equation.length()){
int nextpos = NextPos(equation, i);
if(nextpos == string::npos)
nextpos = equation.length();
if(equation[nextpos - 1] == 'x'){
string temp = equation.substr(i, nextpos - 1 - i);
if(temp == "+")
countx--;
if(temp == "-")
countx++;
else{
if(temp[0] == '+')
countx -= atoi(temp.substr(1, temp.length() - 1).c_str());
else
countx += atoi(temp.substr(1, temp.length() - 1).c_str());
}
}
else{
string temp = equation.substr(i, nextpos - i);
if(temp[0] == '+')
sum += atoi(temp.substr(1, temp.length() - 1).c_str());
else
sum -= atoi(temp.substr(1, temp.length() - 1).c_str());
}
i = nextpos;
}
if(countx == 0 && sum == 0)
return "Infinite solutions";
if(countx == 0 && sum != 0)
return "No solution";
int value = sum / countx;
return "x=" + to_string(value);
}
};
|
