oneDist.cpp

#include <iostream>
#include <string>
#include <cassert>
using namespace std;

bool equal(string& s, int i, string& t, int j) {
  while (i < s.size() && j < t.size() && s[i] == t[j]) {
    i++;
    j++;
  }
  //cout << "i: " << i << ", j: " << j << endl;
  return (i == s.size() && j == t.size());
}

bool oneDist(string& s, string& t) {
  int i = 0; int j = 0;
  while (i < s.size() && j < t.size() && s[i] == t[j]) {
    i++;
    j++;
  }
  return equal(s, i, t, j) || equal(s, i+1, t, j+1) ||
         equal(s, i+1, t, j) || equal(s, i, t, j+1);
}

void test(const char* a, const char *b, bool expected) {
  string strA = a;
  string strB = b;
  //cout << strA << " vs. " << strB << endl;
  assert(oneDist(strA, strB) == expected);
}

int main() {
  test("abc", "abc", true);
  test("abc", "abYc", true);
  test("abXc", "abc", true);
  test("abXc", "abYc", true);
  test("abc", "abcY", true);
  test("abcX", "abc", true);
  test("Xabc", "abc", true);
  test("abc", "Yabc", true);
  test("aXbc", "abYc", false);
  test("abc", "abcYYY", false);
  test("abcXXX", "abc", false);
  test("abcXXX", "abcYYY", false);
  return 0;
}