438. Find All Anagrams in a String

/**
 * @param {string} s
 * @param {string} p
 * @return {number[]}
 */
var findAnagrams = function (s, p) {
  const cntS = new Array(26).fill(0)
  const cntP = new Array(26).fill(0)
  const ans = []
  const n = s.length
  for (const c of p) {
    cntP[c.charCodeAt() - 'a'.charCodeAt()]++
  }
  for (let right = 0; right < n; right++) {
    // 明确写出左端点，不容易出错
    const left = right - p.length + 1
    cntS[s[right].charCodeAt() - 'a'.charCodeAt()]++
    if (left < 0) {
      continue
    }
    if (_.isEqual(cntS, cntP)) {
      ans.push(left)
    }
    cntS[s[left].charCodeAt() - 'a'.charCodeAt()]--
  }
  return ans
}