<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">題目：</span>

Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".

解答1：

錯誤：無法解決較大資料的轉換

/**
 * @param {string} a
 * @param {string} b
 * @return {string}
 */
var addBinary = function(a, b) {
    var array_a = parseInt(a,2);
    var array_b = parseInt(b,2);
    var result = array_a + array_b;
    var resultStr = result.toString(2);
    return resultStr;
};
 

解答2：

正確：

<pre name="code" class="javascript">/**
 * @param {string} a
 * @param {string} b
 * @return {string}
 */
var addBinary = function(a, b) {
    var array_a = a.split("").reverse();
    var array_b = b.split("").reverse();
    
    var resultArray = [];
    var stepIn = 0;
    
    for(var i = 0;i<array_a.length||i<array_b.length||stepIn;i++){
        var a_i = parseInt(array_a[i])||0;
        var b_i = parseInt(array_b[i])||0;
        var result_i = a_i + b_i + stepIn;
        if(result_i == 0){
            resultArray[i] = 0;
            stepIn = 0;
        }else if(result_i == 1){
            resultArray[i] = 1;
            stepIn = 0;
        }else if(result_i == 2){
            resultArray[i] = 0;
            stepIn = 1;
        }else{
            resultArray[i] = 1;
            stepIn = 1;
        }
    }
    resultArray = resultArray.reverse();

    var resultStr = "";
    // resultStr = resultArray.join("");
    for(i = 0;i<resultArray.length;i++){
        resultStr +=resultArray[i];
    }
    return resultStr;
};