剑指offer_05_替换空格【javascript】

请实现一个函数，把字符串 s 中的每个空格替换成"%20"。 例如：

输入：s = "We are happy."
输出："We%20are%20happy."

题解

var replaceSpace = function(s) {
    s = s.split("");
    let oldLen = s.length;
    let spaceCount = 0;
    for (let i = 0; i < oldLen; i++) {
        if (s[i] === ' ') spaceCount++;
    }
    s.length += spaceCount * 2;
    for (let i = oldLen - 1, j = s.length - 1; i >= 0; i--, j--) {
        if (s[i] !== ' ') {
             s[j] = s[i];
        } else {
            s[j - 2] = '%';
            s[j - 1] = '2';
            s[j] = '0';
            j -= 2;
        }
    }
    return s.join('');
};