Merge pull request doocs#34 from KongJHong/master

Add Solution 020 [CPP]

Author: yanglbme

solution/020.Valid Parentheses/README.md

@@ -42,7 +42,10 @@
 ### 解法
 遍历 string，遇到左括号，压入栈中；遇到右括号，从栈中弹出元素，元素不存在或者元素与该右括号不匹配，返回 false。遍历结束，栈为空则返回 true，否则返回 false。
 
-```java
+因为字符串只包含"(){}[]",也可以进行特殊处理，用映射来做
+
+#### java
+```
 class Solution {
     public boolean isValid(String s) {
         if (s == null || s == "") {
@@ -80,4 +83,86 @@ class Solution {
         return a == ')' || a == ']' || a == '}';
     }
 }
+```
+
+#### C++
+```
+
+class Solution {
+public:
+    bool isValid(string s) {
+        stack<char> _stack;
+        int len = s.length();
+        if(len == 0)return true;
+        char ch;
+        for(int i= 0;i<len;i++)
+        {
+            if(s[i] == '{' ||s[i] == '['||s[i] == '(' )
+            {
+                _stack.push(s[i]);
+            }
+            if(s[i] == '}')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '{')return false;
+                else _stack.pop();
+                
+            }
+            else if(s[i] == ']')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '[')return false;
+                else _stack.pop();
+            }
+            else if(s[i] == ')')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '(')return false;
+                else _stack.pop();
+            }         
+        }
+        
+        if(!_stack.empty())return false;
+        
+        return true;
+        
+    }
+};
+
+//特殊
+class Solution {
+public:
+    bool isValid(string s) {
+        map<char,int> m={
+            {'[',1},
+            {']',-1},
+            {'{',2},
+            {'}',-2},
+            {'(',3},
+            {')',-3}
+        };
+        stack<int> sk;
+        for(int i=0;i<s.length();i++){
+            if(m[s[i]]<0 ){
+                if(!sk.empty() && sk.top()==(-m[s[i]])){
+                    sk.pop();
+                }else{
+                    return false;
+                }
+            }else{
+                sk.push(m[s[i]]);
+            }
+        }
+        if(sk.empty())
+            return true;
+        return false;
+    }
+};
+
 ```

solution/020.Valid Parentheses/Solution.cpp

@@ -0,0 +1,79 @@
+class Solution {
+public:
+    bool isValid(string s) {
+        stack<char> _stack;
+        int len = s.length();
+        if(len == 0)return true;
+        char ch;
+        for(int i= 0;i<len;i++)
+        {
+            if(s[i] == '{' ||s[i] == '['||s[i] == '(' )
+            {
+                _stack.push(s[i]);
+            }
+            if(s[i] == '}')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '{')return false;
+                else _stack.pop();
+                
+            }
+            else if(s[i] == ']')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '[')return false;
+                else _stack.pop();
+            }
+            else if(s[i] == ')')
+            {
+                if(_stack.empty())return false;
+                else ch = _stack.top();
+                
+                if(ch != '(')return false;
+                else _stack.pop();
+            }         
+        }
+        
+        if(!_stack.empty())return false;
+        
+        return true;
+        
+    }
+};
+
+
+
+-----------------
+//特殊
+class Solution {
+public:
+    bool isValid(string s) {
+        map<char,int> m={
+            {'[',1},
+            {']',-1},
+            {'{',2},
+            {'}',-2},
+            {'(',3},
+            {')',-3}
+        };
+        stack<int> sk;
+        for(int i=0;i<s.length();i++){
+            if(m[s[i]]<0 ){
+                if(!sk.empty() && sk.top()==(-m[s[i]])){
+                    sk.pop();
+                }else{
+                    return false;
+                }
+            }else{
+                sk.push(m[s[i]]);
+            }
+        }
+        if(sk.empty())
+            return true;
+        return false;
+    }
+};