leetcode new problems

leetcode/lc20/ValidParantheses1.cpp

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    bool isValid(string s) {
+        stack<char> st;
+        unordered_map<char,char> mapping = {{')','('}, {'}','{'}, {']','['}};
+        for(char c: s){
+                if(mapping.find(c) == mapping.end()) st.push(c);
+                else if(!st.empty() && mapping[c] == st.top()) st.pop();
+                else return false;
+
+        }
+        return st.empty();
+
+
+
+    }
+};