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438. Find All Anagrams in a String
Medium
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.
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".
Constraints:
1 <= s.length, p.length <= 3 * 104sandpconsist of lowercase English letters.
Solution
function findAnagrams(s: string, p: string): number[] {
const map: number[] = new Array(26).fill(0)
for (let i = 0; i < p.length; ++i) {
map[p.charCodeAt(i) - 'a'.charCodeAt(0)]++
}
const res: number[] = []
let i: number = 0
let j: number = 0
while (i < s.length) {
const idx: number = s.charCodeAt(i) - 'a'.charCodeAt(0)
// Add the new character
map[idx]--
// If the length is greater than window's length, pop the left character in the window
if (i >= p.length) {
map[s.charCodeAt(j++) - 'a'.charCodeAt(0)]++
}
let finish: boolean = true
for (let k = 0; k < 26; k++) {
// If it is not an anagram of string p
if (map[k] !== 0) {
finish = false
break
}
}
if (i >= p.length - 1 && finish) {
res.push(j)
}
i++
}
return res
}
export { findAnagrams }