string isBalanced(string s) {
stack<char> stk;


for (int i = 0 ; i<s.length(); i++) 
{
if(!stk.empty())
{
char tp  =stk.top();

if( (tp == '{' && s[i] == '}')||(tp == '(' && s[i] == ')') ||( tp == '[' && s[i] == ']'))
{
stk.pop();

}else {
stk.push(s[i]);
}
}else {
stk.push(s[i]);

}

}