insert m into n, bit position i to j

bit_insert.cpp

#include <iostream>

using namespace std;

// see http://d.hatena.ne.jp/kobapan/20090208/1281901941                                                                                                    
int strbin2i (const std::string &s) {
  int out = 0;
  for (int i = 0, size = s.size() ; i < size ; ++i ) {
    out *= 2;
    out += ((int)s[i] == 49) ? 1 : 0;
  }
  return out;
}

int insert(int n, int m, int i, int j) {
  int left_more_j_of_n = (n & ~((1 << j) - 1));
  int right_more_i_of_n = (n & ~((1 << i + 1) - 1));
  return (left_more_j_of_n | right_more_i_of_n | (m << i));
}

int main() {
  int n = strbin2i("10000000000");
  int m = strbin2i("10011");
  int ans = insert(n, m, 2, 6);
  cout << ans << endl;

  return 0;
}