如何检查2个字符串是否包含相等的字符？

Question

im trying to make a function that will take two strings from user and check if they contain equal characters. For example test and set , both these strings contain the letter t and s so the output should be true . I started a few weeks ago so im having some trouble with executing the code correctly. Can someone please explain what im doing wrong? thanks everyone

#include <iostream>
#include <string>

bool equal(char first, char second);

using namespace std;

int main() {
  string first;

  string second;

  bool equal;
  int se;
  cout << "enter a string " << endl;
  getline(cin, first);
  cout << "enter another string " << endl;
  getline(cin, second);
  equal(first ,second);

  if (equal) {
    cout << "strings are equal" << endl;
  } else if (!equal) {
    cout << "strings not " << endl;
  }
  return 0;
}

bool equal(string first, string second) {
  for (int i = 0; i < first.length(); i++) {
    for (int j = j + 1; i < second.length(); i++) {
      if (i == j)
        return true;
      else
        return false;
    }
  }
}

Answer 1

You may use

bool contain_same_letters(const std::string& lhs, const std::string& rhs)
{
    return std::set<char>(lhs.begin(), lhs.end())
        == std::set<char>(rhs.begin(), rhs.end());
}

Answer 2

The inner loop of equal() is wrong, it should be:

for (int j = 0; j < second.size(); j++)
    if (first[i] == second[j])

instead of

for (int j = j + 1; i < second.length(); i++) {
    if (i == j)

Answer 3

We can guess at the error message (don't make us, though!). You declared bool equal(char first, char second); but defined bool equal(string first, string second) . Hence, when you try to call it, the compiler complains about an incorrect argument type.

Your next problem will be at runtime, because your implementation of equal isn't working right. But this is an algorithm problem; you should think about how it should work. You can't return when there's one match, but you can return when there's one mis-match.

There is also a smart trick by using the functions from <algorithm> but I won't give that away. One hint, though: it's hard to compare "test" and "set" because the letters are in a different order.