1763.js

var longestNiceSubstring = function (s) {
    this.maxPos = 0
    this.maxLen = 0

    let types = 0
    for (let i = 0; i < s.length; ++i) {
        types |= 1 << (s[i].toLowerCase().charCodeAt() - 'a'.charCodeAt())
    }
    types = bitCount(types)
    for (let i = 1; i <= types; ++i) {
        check(s, i)
    }
    return s.slice(maxPos, maxPos + maxLen)
}

const check = (s, typeNum) => {
    const lowerCnt = new Array(26).fill(0)
    const upperCnt = new Array(26).fill(0)
    let cnt = 0
    for (let l = 0, r = 0, total = 0; r < s.length; ++r) {
        let idx = s[r].toLowerCase().charCodeAt() - 'a'.charCodeAt()
        if ('a' <= s[r] && s[r] <= 'z') {
            ++lowerCnt[idx]
            if (lowerCnt[idx] === 1 && upperCnt[idx] > 0) {
                ++cnt
            }
        } else {
            ++upperCnt[idx]
            if (upperCnt[idx] === 1 && lowerCnt[idx] > 0) {
                ++cnt
            }
        }
        total += (lowerCnt[idx] + upperCnt[idx]) === 1 ? 1 : 0
        while (total > typeNum) {
            idx = s[l].toLowerCase().charCodeAt() - 'a'.charCodeAt()
            total -= (lowerCnt[idx] + upperCnt[idx]) === 1 ? 1 : 0
            if ('a' <= s[l] && s[l] <= 'z') {
                --lowerCnt[idx]
                if (lowerCnt[idx] === 0 && upperCnt[idx] > 0) {
                    --cnt
                }
            } else {
                --upperCnt[idx]
                if (upperCnt[idx] === 0 && lowerCnt[idx] > 0) {
                    --cnt
                }
            }
            ++l
        }
        if (cnt === typeNum && r - l + 1 > maxLen) {
            maxPos = l
            maxLen = r - l + 1
        }
    }
}

var bitCount = function (n) {
    let ret = 0
    while (n) {
        n &= n - 1
        ret++
    }
    return ret
}

/* 
    2022/02/01
    95 25
    滑动窗口
*/