A short program to find the First & Follow of a Grammar in CPP (82 Lines of Code)

Find First & Follow in CPP

#include<bits/stdc++.h>
using namespace std;
int main() {
	string a[5];
	for(int i = 0; i < 5; i++) cin>>a[i];
	map <char, string> s;
	unordered_map <char, vector <char>> first, follow, t;
	for(int i = 0; i < 5; i++) {
		cout<<a[i]<<endl;
		string h="";
		for(int j = 3; j < a[i].size(); j++) {
			h+=a[i][j];
		}
		s[a[i][0]] = h;
	}
	for(auto i:s) {
		bool find = true;
		for(auto j:i.second) {
			if(j == '|') {
				find = true;
			} else if(j == '(') {
				first[i.first].push_back('(');
				continue;
			} else if(j >= 65 && j <= 90 && find) {
				find = false;
				first[i.first].insert(first[i.first].end(), first[j].begin(), first[j].end());
			} else if(find) {
				first[i.first].push_back(j);
				find = false;
			}
		}
	}
	follow['E'].push_back('$');
	for(auto i= s.end(); i!= s.begin(); i--) {
		for(auto find_i:s) {
			bool found = false;
			for(auto i_string:find_i.second) {
				if(found) {
					found = false;
					if(i_string >= 65 && i_string <= 90) {
						follow[i->first].insert(follow[i->first].end(), first[i_string].begin(), first[i_string].end());
						for(auto p : first[i_string]) {
							{
								if(p == '(') {
									found = true;
									continue;
								}
								follow[i->first].push_back(p);
							}						
						}
					} else if(i_string == '|' || i_string == '.') {
						follow[i->first].insert(follow[i->first].end(), follow[find_i.first].begin(), follow[find_i.first].end());
					} else {
						follow[i->first].push_back(i_string);
					}
				}
				if(i_string == i->first) {
					found = true;
				}
			}
		}
	}
	cout<<"First: \n";
	for(auto i:first) {
		cout<<i.first<<" : ";
		for(auto j:i.second) {
			cout<<j<<" ";
		}cout<<endl;
	}
	cout<<"Follow: \n";
	for(auto i:follow) {
		cout<<i.first<<" : ";
		sort( i.second.begin(), i.second.end() );
		i.second.erase( unique( i.second.begin(), i.second.end() ), i.second.end() );
		for(auto j:i.second) {
			if(j == '(')
				continue;
			cout<<j<<" ";
		}
		cout<<endl;
	}
}


// Conditions for input:
// 1. Epsilon is represented as '('. So if you want to use '(',')', consider using '[',']'
// 2. The Variable Names should be in reverse alphabetical order due to the usage of maps.
// For example, if the Start Symbol is S, the further variables should be named anywhere from [A, R]. 
// After every production set defined, add a '.' to signify its end. Except for Epsilon '('
// 3. Avoid white spaces in your input. Do not leave spaces after left-hand declaration of variable.
// E -> A -- this is wrong
// E->A -- this is right. Why? Notice line 11 where I'm converting the input grammar into a map
// 4. Terminal names can only be of one character

// An example input:
// E->CD.
// D->+CD.|(
// C->AB.
// B->*AB.|(
// A->i.|[E].

An example input and output for the following program.
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