[67] 二进制求和

/**
 * @param {string} a
 * @param {string} b
 * @return {string}
 */
var addBinary = function (a, b) {
    let shortList = []
    let longList = []
    if (b.length > a.length) {
        shortList = a.split('').reverse();
        longList = b.split('').reverse();
    } else {
        longList = a.split('').reverse();
        shortList = b.split('').reverse();
    }
    longList.push('0');
    for (let i = 0; i < b.length; i++) {
        if (shortList[i] === '1') {
            let j = i;
            for (; j < longList.length; j++) {
                if (longList[j] === '0') {
                    longList[j] = '1';
                    break;
                }
                longList[j] = '0';
            }
        }
    }
    const ans = longList.reverse().join('')
    return ans.slice(0, 1) === '1' ? ans : ans.slice(1);
};