#C++11 code, 386 characters# #include #include using namespace std;using =map<int,string>;using X=const char; format1(Xp,Xs,_ k=()){ r;while(*p!='{'){if(!*p||!s){returnp==*s?k:r;}if(p++!=s++)return r;}int v=0;while(++p!='}'){v=v10+(*p-48);}p++;if(k.find(v)!=k.end()){return format1((k[v]+p).c_str(),s,k);}while((r=format1(p,s,k)).empty()){k[v]+=*s++;if(!s){returnp==*s?k:r;}}return r;}

for (auto v : format1("{1} {2}", "one two")){
    cout << v.first << "=" << v.second << endl;
}

example2:

auto v = format1("{1} {2}", "one two");
cout << v[1] << " and " << v[2] << endl;

The patterns are in decimal representation, inputs bigger than MAXINT will overflow but still works.

#include <string>
#include <map>
using namespace std;

using res = map<int,string>;

res format1(const char* p, const char* s, res k=res()){
    res r; // intermediate result, empty until the end
    // match until first '{'
    while (*p != '{'){
        if (!*p || !*s){
            // exit case
            return ((*p == *s) ? k : r); // == 0
        }
        if (*p++ != *s++)
               return r;
    }
    
    // *p == '{'
    int v = 0;
    while(*++p != '}'){
        v = v*10 + (*p - '0');
    }
    p++; // advance past '}'

    // match back-references
    if (k.find(v) != k.end()){
       return format1((k[v]+p).c_str(), s, k);
    }

    // recursive search
    while ( (r=format1(p, s, k)).empty() ){
        k[v] += *s++;
        if (!*s){
            return *p == *s ? k : r;
        }
    }
    return r;
}

#C++11 code, 386 characters#

#include <string>
#include <map>
using namespace std;using _=map<int,string>;using X=const char;_ format1(X*p,X*s,_ k=_()){_ r;while(*p!='{'){if(!*p||!*s){return*p==*s?k:r;}if(*p++!=*s++)return r;}int v=0;while(*++p!='}'){v=v*10+(*p-48);}p++;if(k.find(v)!=k.end()){return format1((k[v]+p).c_str(),s,k);}while((r=format1(p,s,k)).empty()){k[v]+=*s++;if(!*s){return*p==*s?k:r;}}return r;}

for (auto v : format1("{1} {2}", "one two")){
    cout << v.first << "=" << v.second << endl;
}

Example 2:

auto v = format1("{1} {2}", "one two");
cout << v[1] << " and " << v[2] << endl;

The patterns are in decimal representation, inputs bigger than MAXINT will overflow but it still works.

#include <string>
#include <map>
using namespace std;

using res = map<int,string>;

res format1(const char* p, const char* s, res k=res()){
    res r; // intermediate result, empty until the end
    // match until first '{'
    while (*p != '{'){
        if (!*p || !*s){
            // exit case
            return ((*p == *s) ? k : r); // == 0
        }
        if (*p++ != *s++)
               return r;
    }
    
    // *p == '{'
    int v = 0;
    while(*++p != '}'){
        v = v*10 + (*p - '0');
    }
    p++; // advance past '}'

    // match back-references
    if (k.find(v) != k.end()){
       return format1((k[v]+p).c_str(), s, k);
    }

    // recursive search
    while ( (r=format1(p, s, k)).empty() ){
        k[v] += *s++;
        if (!*s){
            return *p == *s ? k : r;
        }
    }
    return r;
}

1=one 2=two

one and two

The patterns are in decimal representation, numbers bigger than MAXINT will overflow but still works.

1=one
2=two

one and two

The patterns are in decimal representation, inputs bigger than MAXINT will overflow but still works.