[JS] Find All Anagrams in a String

🔒 문제 (LeetCode 438)

Given two strings s and p, return an array of all the start indices of p's anagrams in s. You may return the answer in any order.

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.

Constraints:

• 1 <= s.length, p.length <= 3 * 104
• s and p consist of lowercase English letters.

 

🌊 입출력

Example 1:

Input: s = "cbaebabacd", p = "abc"
Output: [0,6]
Explanation:
The substring with start index = 0 is "cba", which is an anagram of "abc".
The substring with start index = 6 is "bac", which is an anagram of "abc".

Example 2:

Input: s = "abab", p = "ab"
Output: [0,1,2]
Explanation:
The substring with start index = 0 is "ab", which is an anagram of "ab".
The substring with start index = 1 is "ba", which is an anagram of "ab".
The substring with start index = 2 is "ab", which is an anagram of "ab".

 

 

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🔑 해결

🌌 알고리즘 -  sliding window

/**
 * @param {string} s
 * @param {string} p
 * @return {number[]}
 */
var findAnagrams = function(s, p) {
    const result = [];
    let countChars = {};
    
    for(let char of p) {
        if(char in countChars) {
            countChars[char]++;
        } else countChars[char] = 1;
    }
    
    let l = 0;
    let r = 0;
    let count = p.length;
    
    while(r < s.length) {
        if(countChars[s[r]] > 0) count--;
        
        countChars[s[r]]--;
        r++;
        
        if(count === 0) result.push(l);
        
        if(r - l === p.length) {
            if(countChars[s[l]] >= 0) count++;
            
            countChars[s[l]]++;
            l++;
        }
    }
    
    return result;
};