列出排列

Question

我正在尝试列出所有三个字母的排列,这是我的代码 -

  window.permute = function(){
    var alphabet = "abcdefghijklmnopqrstuvwxyz";
    var searchTerm ="aaa";
    var position = 2; 
    changeString(searchTerm, position); 
}

window.changeString = function(searchTerm, position){
    if (position <0){
        alert(newString);

    return; 
    }
    var alphabet = "abcdefghijklmnopqrstuvwxyz"
    for (j=0; j < 26;j++){
        var newString = searchTerm.substr(0, position) + alphabet[j] + searchTerm.substr(position+1);
        var newPosition = position -1; 
        changeString(newString,newPosition);
    }
    return;
}

它不起作用,我不知道为什么 - 有人可以帮忙吗？

Answer 1

alert(newString);

newString没有在那里定义。相反，您应该使用传递的参数：

alert(searchTerm);

编辑：我不完全确定你的方法。看起来过于复杂了。这似乎有效。我知道您宁愿让自己的代码工作，但这也许可以帮助您解决问题。我不太明白你的substr意思。

http://jsfiddle.net/NUG2A/2/

var alphabet = "abc"; // shortened to save time

function permute(text) {
    if(text.length === 3) { // if length is 3, combination is valid; alert
        console.log(text); // or alert
    } else {
        var newalphabet = alphabet.split("").filter(function(v) {
            return text.indexOf(v) === -1;
        }); // construct a new alphabet of characters that are not used yet
            // because each letter may only occur once in each combination

        for(var i = 0; i < newalphabet.length; i++) {
            permute(text + newalphabet[i]); // call permute with current text + new
                                            // letter from filtered alphabet
        }
    }
}

permute("");

这将导致调用以下内容：

permute("");
permute("a");
permute("ab");
permute("abc"); // alert
permute("ac");
permute("acb"); // alert
permute("b");
// ...