Parse string and replace - c++

Question

How i could convert this javascript code to c++
key = {"|1|":"A","|2|":"B","|4|":"C","|3|":"D"}
y = "|1||2||3||4|"
for (i in key)
y = y.replace(i,key[i])
console.log(y)
output: ABDC
I got the "decoding key" in a std::string like:
std::string key = "{\"|1|\":\"A\",\"|2|\":\"B\",\"|3|\":\"D\",\"|4|\":\"C\"}";
Based on the properties of this key do a string replace in my_string.
Example:
std::string key = "{\"|1|\":\"A\",\"|2|\":\"B\",\"|3|\":\"D\",\"|4|\":\"C\"}";
std::string my_string = "|1||2||3||4|";
// . . .
Replace in my_string |1| to A, |2| to B, |3| to D, |4| to C
|1| to A, |2| to B ... etc comes from the std::string key
Then my_string now is ABDC.
Do i need to convert the std:: string key to another data type? I mean something similar to an object like on javascript, im not familiar with c++.

Answer 1

Equivalents of java dictionnary is map or unordered_map
As for your json question, you need a library to parse json, I recommend the excellent one from Professor Lemire (github lemire)
I just wrote you a simple json parser for you. Note that you will need to compile with c++1z or you will get the warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z
g++ -std=c++1z test.cpp && ./a.out
#include <unordered_map>
#include <iostream>
#include <sstream>
using namespace std;
void jsonDecode(unordered_map <string, char> &m, string s) {
constexpr char delimiter = '"';
for (int i = 0; i < s.size(); ) {
if (s[i++] == delimiter) {
stringstream ss;
while (s[i] != delimiter)
ss << s[i++];
string key = ss.str();
++i;
while (s[i] != delimiter) i++;
char value = s[++i];
m[key] = value;
i+=2;
}
}
}
int main(void) {
unordered_map <string, char> m;
string s = R"({"|1|":"A","|2|":"B","|3|":"D","|4|":"C"})";
jsonDecode(m, s);
string y = "|1||2||3||4|";
for (auto &[k,v] : m)
y.replace(y.find(k), k.size(), string(1, v));
cout << y << endl;
return 0;
}
output:
ABDC
You can read about replace method here

Answer 2

Here is a direct "translation" to C++:
#include<iostream>
#include<string>
#include<unordered_map>
int main()
{
std::unordered_map<std::string, std::string> dictionary = { {"|1|","A"} , {"|2|", "B"}, {"|4|", "C"}, {"|3|", "D"} };
std::string y = "|1||2||3||4|";
size_t pos;
for (auto& a : dictionary) {
while((pos = y.find(a.first)) != std::string::npos)
y.replace(pos, a.first.length(), a.second);
}
std::cout << y << std::endl;
return 0;
}