345. 反转字符串中的元音字母

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leading to the advanced question

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方案一: 对撞指针

var reverseVowels = function(s) {
    const n = s.length;
    const arr = Array.from(s);
    let i = 0, j = n - 1;
    while (i < j) {
        while (i < n && !isVowel(arr[i])) {
            ++i;
        }
        while (j > 0 && !isVowel(s[j])) {
            --j;
        }
        if (i < j) {
            swap(arr, i, j);
            ++i;
            --j;
        }
    }
    return arr.join('');
}

const isVowel = (ch) => {
    return "aeiouAEIOU".indexOf(ch) >= 0;
}

const swap = (arr, i, j) => {
    const temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}