MathQuestion.js

var valid_list = [];
var diffCount = function(a, b) {
    var result = 0;
    if(parseInt(a/100000)%10 != parseInt(b/100000)%10) result++;
    if(parseInt(a/10000)%10 != parseInt(b/10000)%10) result++;
    if(parseInt(a/1000)%10 != parseInt(b/1000)%10) result++;
    if(parseInt(a/100)%10 != parseInt(b/100)%10) result++;
    if(parseInt(a/10)%10 != parseInt(b/10)%10) result++;
    if(parseInt(a/1)%10 != parseInt(b/1)%10) result++;
    return result;
};
for(var i = 0; i < 1000000; i++) {
    var valid = true;
    for(var j = 0; j < valid_list.length; j++){
        if(diffCount(valid_list[j], i)<2) {
            valid = false;
            break;
        }
    }
    if(valid) {
       valid_list.push(i);
    }
}
alert(valid_list.length);