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Commit d8fdeb6

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Merge pull request #34 from KongJHong/master
Add Solution 020 [CPP]
2 parents a68cf97 + 5b562ea commit d8fdeb6

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2 files changed

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lines changed

2 files changed

+165
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lines changed

‎solution/020.Valid Parentheses/README.md‎

Lines changed: 86 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -42,7 +42,10 @@
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### 解法
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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。
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```java
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因为字符串只包含"(){}[]",也可以进行特殊处理,用映射来做
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#### java
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```
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class Solution {
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public boolean isValid(String s) {
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if (s == null || s == "") {
@@ -80,4 +83,86 @@ class Solution {
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return a == ')' || a == ']' || a == '}';
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}
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}
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```
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#### C++
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```
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class Solution {
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public:
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bool isValid(string s) {
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stack<char> _stack;
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int len = s.length();
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if(len == 0)return true;
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char ch;
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for(int i= 0;i<len;i++)
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{
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if(s[i] == '{' ||s[i] == '['||s[i] == '(' )
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{
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_stack.push(s[i]);
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}
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if(s[i] == '}')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '{')return false;
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else _stack.pop();
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}
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else if(s[i] == ']')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '[')return false;
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else _stack.pop();
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}
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else if(s[i] == ')')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '(')return false;
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else _stack.pop();
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}
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}
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if(!_stack.empty())return false;
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return true;
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}
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};
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//特殊
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class Solution {
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public:
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bool isValid(string s) {
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map<char,int> m={
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{'[',1},
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{']',-1},
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{'{',2},
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{'}',-2},
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{'(',3},
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{')',-3}
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};
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stack<int> sk;
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for(int i=0;i<s.length();i++){
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if(m[s[i]]<0 ){
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if(!sk.empty() && sk.top()==(-m[s[i]])){
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sk.pop();
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}else{
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return false;
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}
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}else{
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sk.push(m[s[i]]);
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}
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}
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if(sk.empty())
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return true;
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return false;
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}
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};
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```
Lines changed: 79 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,79 @@
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class Solution {
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public:
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bool isValid(string s) {
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stack<char> _stack;
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int len = s.length();
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if(len == 0)return true;
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char ch;
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for(int i= 0;i<len;i++)
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{
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if(s[i] == '{' ||s[i] == '['||s[i] == '(' )
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{
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_stack.push(s[i]);
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}
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if(s[i] == '}')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '{')return false;
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else _stack.pop();
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}
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else if(s[i] == ']')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '[')return false;
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else _stack.pop();
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}
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else if(s[i] == ')')
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{
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if(_stack.empty())return false;
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else ch = _stack.top();
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if(ch != '(')return false;
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else _stack.pop();
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}
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}
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if(!_stack.empty())return false;
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return true;
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}
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};
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-----------------
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//特殊
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class Solution {
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public:
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bool isValid(string s) {
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map<char,int> m={
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{'[',1},
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{']',-1},
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{'{',2},
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{'}',-2},
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{'(',3},
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{')',-3}
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};
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stack<int> sk;
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for(int i=0;i<s.length();i++){
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if(m[s[i]]<0 ){
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if(!sk.empty() && sk.top()==(-m[s[i]])){
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sk.pop();
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}else{
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return false;
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}
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}else{
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sk.push(m[s[i]]);
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}
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}
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if(sk.empty())
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return true;
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return false;
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}
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};

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