#include <iostream>
#include <string>
using std::cout;
using std::endl;
using std::string;
string space2underscore(string s) {
for (string::iterator it = s.begin(); it != s.end(); it++) {
if (*it == ' ') {
*it = '_';
}
}
return s;
}
int main()
{
string s = "c c++ php java";
s = space2underscore(s);
cout << s << endl;
return 0;
}
/*
run:
c_c++_php_java
*/