Determine whether a one-to-one character mapping exists from one string, s1, to another string, s2. For example, given s1 = abc and s2 = bcd, print "true" into stdout since we can map each character in "abc" to a character in "bcd". Given s1 = foo and s2 = bar, print "false" since the character ‘o’ cannot map to two characters. But given s1 = bar and s2 = foo, print "true" since each character in "bar" can be mapped to a character in "foo".
