13.Roman_to_Integer.cpp

/*
    written by Pankaj Kumar.
    country:-INDIA
*/
typedef long long ll ;


/* ascii value
A=65,Z=90,a=97,z=122
*/

/*  --------------------MAIN PROGRAM----------------------------*/
// to run ctrl+b
const ll INF=1e18;
const ll mod1=1e9+7;
const ll mod2=998244353;
// Techniques :
// divide into cases, brute force, pattern finding
// sort, greedy, binary search, two pointer
// transform into graph

// Experience :
// Cp is nothing but only observation and mathematics.


//Add main code here

class Solution
{
public:
    int romanToInt(string s)
    {
        map<char,int> m;
        m['I']=1;
        m['V']=5;
        m['X']=10;
        m['L']=50;
        m['C']=100;
        m['D']=500;
        m['M']=1000;
        int ans=0;
        for(int i=0;i<s.size();i++)
        {
            if(i+1<s.size()&&m[s[i]]<m[s[i+1]])
            {
                ans+=m[s[i+1]]-m[s[i]];
                i++;
            }
            else
                ans+=m[s[i]];
        }
        return ans;
    }
};

/* -----------------END OF PROGRAM --------------------*/
/*
* stuff you should look before submission
* constraint and time limit
* int overflow
* special test case (n=0||n=1||n=2)
* don't get stuck on one approach if you get wrong answer
*/