242. Valid Anagram #

Problem #

Given two strings s and t , write a function to determine if t is an anagram of s.

Example 1:

Input: s = "anagram", t = "nagaram"
Output: true

Example 2:

Input: s = "rat", t = "car"
Output: false

Note:

You may assume the string contains only lowercase alphabets.

Follow up:

What if the inputs contain unicode characters? How would you adapt your solution to such case?

Problem Summary #

Given 2 strings s and t, if every letter in t exists in s, output true; otherwise output false.

Solution Approach #

This problem can be solved using a counting table. First store each letter in s in an array with a capacity of 26, where each index corresponds to one of the 26 letters in order. Each letter in s corresponds to a letter in the table, and the count is incremented by 1 each time it appears. Then scan the string t, and decrement the count in the table by one each time a letter appears. If all letters appear, the final values in the table must all be 0. Finally, check whether all values in the table are 0; if any non-0 number exists, output false.

Code #

package leetcode

// Solution 1
func isAnagram(s string, t string) bool {
	alphabet := make([]int, 26)
	sBytes := []byte(s)
	tBytes := []byte(t)
	if len(sBytes) != len(tBytes) {
		return false
	}
	for i := 0; i < len(sBytes); i++ {
		alphabet[sBytes[i]-'a']++
	}
	for i := 0; i < len(tBytes); i++ {
		alphabet[tBytes[i]-'a']--
	}
	for i := 0; i < 26; i++ {
		if alphabet[i] != 0 {
			return false
		}
	}
	return true
}

// Solution 2
func isAnagram1(s string, t string) bool {
	hash := map[rune]int{}
	for _, value := range s {
		hash[value]++
	}
	for _, value := range t {
		hash[value]--
	}
	for _, value := range hash {
		if value != 0 {
			return false
		}
	}
	return true
}