Added 13.Roman_to_Integer.cpp

C++/Roman_to_Integer.cpp

@@ -0,0 +1,60 @@
+#include <string>
+
+/*** 13. Roman to Intege (Easy)***/
+
+/*
+Symbol Value
+I 1
+V 5
+X 10
+L 50
+C 100
+D 500
+M 1000
+*/
+
+class Solution {
+public:
+ int romanToInt(string s) {
+ int current = 0, last =0;
+ int sum=0;
+ for(int i=0;i<s.length();i++){
+ switch(s[i]){
+ case 'I':
+ current = 1;
+ break;
+ case 'V':
+ current = 5;
+ break;
+ case 'X':
+ current = 10;
+ break;
+ case 'L':
+ current = 50;
+ break;
+ case 'C':
+ current = 100;
+ break;
+ case 'D':
+ current = 500;
+ break;
+ case 'M':
+ current = 1000;
+ break;
+ default:
+ break;
+ }
+ sum+=current;
+ /*
+ I can be placed before V (5) and X (10) to make 4 and 9. 
+ X can be placed before L (50) and C (100) to make 40 and 90. 
+ C can be placed before D (500) and M (1000) to make 400 and 900
+ */
+ if(i!=0&&current>last)
+ sum-=2*last;
+ last = current;
+
+ }
+ return sum;
+ }
+};

C++/Valid_Parentheses.cpp

@@ -0,0 +1,58 @@
+#include <list>
+#include <string>
+/*
+Example 1:
+Input: s = "()"
+Output: true
+
+Example 2:
+Input: s = "()[]{}"
+Output: true
+
+Example 3:
+Input: s = "(]"
+Output: false
+
+Example 4:
+Input: s = "([)]"
+Output: false
+
+Example 5:
+Input: s = "{[]}"
+Output: true
+*/
+
+class Solution {
+public:
+ bool isValid(string s) {
+ list<char> open;
+ if(s.length()%2!=0)
+ return false;
+ for(int i=0; i<s.length();i++){
+ if(s[i]=='{'||s[i]=='['||s[i]=='(')
+ open.push_front(s[i]);
+ else{
+ switch(s[i]){
+ case '}':
+ if(open.front()!='{')
+ return false;
+ break;
+ case ']':
+ if(open.front()!='[')
+ return false;
+ break;
+ case ')':
+ if(open.front()!='(')
+ return false;
+ break;
+ default :
+ return true;
+ }
+ open.pop_front();
+ } 
+ }
+ if(open.size()!=0)
+ return false;
+ return true;
+ }
+};

README.md

@@ -201,7 +201,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 
 | # | Title | Solution | Time | Space | Difficulty | Tag | Note |
 | ---- | ------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------- | ------ | ------ | ---------- | ---------------------- | ---- |
-| 020 | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/) | [Python](./Python/20_ValidParentheses.py) | _O(n)_ | _O(n)_ | Easy | Stack | |
+| 020 | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/) | [Python](./Python/20_ValidParentheses.py) [C++](./C++/Vlalid_Parentheses.cpp)  | _O(n)_ | _O(n)_ | Easy | Stack | |
 | 084 | [Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/) | [C++](./C++/Largest-Rectangle-in-Histogram.cpp) | _O(n)_ | _O(n)_ | Hard | Stack |
 | 150 | [Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/) | [Python](./Python/150.EvaluateReversePolishNotation.py) <br> [Java](./Java/evaluate_reverse_polish_notation.java) | _O(n)_ | _O(1)_ | Medium | Stack | |
 | 1047 | [Remove All Adjacent Duplicates In String](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/) | [C++](./C++/remove-all-adjacent-duplicates-in-string.cpp) | _O(n)_ | _O(n)_ | Easy | Stack | |
@@ -309,7 +309,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | 202 | [Happy Number](https://leetcode.com/problems/happy-number) | [Java](./Java/Happy-Number.java) | _O(n^2)_ | _O(n)_ | Easy | Math | |
 | 326 | [Power of Three](https://leetcode.com/problems/power-of-three) | [Java](./Java/Power-of-Three.java) | _O(logn)_ | _O(n)_ | Easy | Math | |
 | 12 | [Integer to Roman](https://leetcode.com/problems/integer-to-roman) | [Java](./Java/integer-to-roman.java) | _O(n)_ | _O(1)_ | Medium | Math | |
-| 13 | [Roman to Integer](https://leetcode.com/problems/roman-to-integer) | [Java](./Java/roman-to-integer.java)  | _O(n)_ | _O(1)_ | Easy | Math | |
+| 13 | [Roman to Integer](https://leetcode.com/problems/roman-to-integer) | [Java](./Java/roman-to-integer.java) <br> [C++](./C++/Roman_to_Integer.cpp)| _O(n)_ | _O(1)_ | Easy | Math | | 
 | 14 | [Arithmetic Subarrays](https://leetcode.com/problems/arithmetic-subarrays/) | [Java](./Java/Arithmetic-Subarrays.java) | _O(m\*n)_ | _O(n)_ | Medium | Math | Pattern Count |
 | 263 | [Ugly Number](https://leetcode.com/problems/ugly-number/) | [Java](./Java/Ugly-Number.java) | _O(n)_ | _O(n)_ | Easy | Math | |