import 'package:test/test.dart';

// Leetcode problem url: https://leetcode.com/problems/isomorphic-strings/

bool isIsomorphic(String string1, String string2) {

Map<String, String> sMap = {};

Map<String, String> tMap = {};

for (int i = 0; i < string1.length; ++i) {

String s = string1[i];

String c = string2[i];

// Both characters are not mapped so far.

if (!sMap.containsKey(s) && !tMap.containsKey(c)) {

sMap[s] = c;

tMap[c] = s;

}

// One of the characters is mapped.

else if (!sMap.containsKey(s) || !tMap.containsKey(c)) {

return false;

}

// Both characters are mapped

else if (sMap[s] != c || tMap[c] != s) {

return false;

}

}

return true;

}

void main() {

test('test case 1', () => expect(isIsomorphic('egg', 'add'), true));

test('test case 2', () => expect(isIsomorphic('foo', 'bar'), false));

test('test case 3', () => expect(isIsomorphic('paper', 'title'), true));

}