2015年6月27日土曜日

開発環境

Data Structures and Algorithms With Javascript (Michael McMillan(著)、O'Reilly Media)のChapter 4(Stacks)、Exercises 1.(No. 2801)を解いてみる。

Exercises 1.(No. 2801)

JavaScript(Emacs)

/*jslint         browser : true, continue : true,
  devel  : true, indent  : 4,    maxerr   : 50,
  newcap : true, nomen   : true, plusplus : false,
  regexp : true, sloppy  : true, vars     : false,
  white  : false
*/

/*global print */
var Stack,
    getPosition,
    expr1 = '2.3 + 23 / 12 + (3.14159 * .24',
    expr2 = '2.3 + 23 / 12 + (3.14159 * .24)',
    expr3 = '2.3 + 23 / 12 + (3.14159 * .24))';

Stack = function () {
    this.data_store = [];
    this.top = 0;
};
Stack.prototype.push = function (element) {
    this.data_store[this.top] = element;
    this.top += 1;
};
Stack.prototype.peak = function () {
    return this.data_store[this.top - 1];
};
Stack.prototype.pop = function () {
    this.top -= 1;
    return this.data_store[this.top];
};
Stack.prototype.clear = function () {
    this.top = 0;
    this.data_store.length = 0;
};
Stack.prototype.length = function () {
    return this.top;
};

getPosition = function (expr) {
    var pos,
        stack = new Stack(),
        ops = expr.split(''),
        i,
        balance,
        op;

    for (i = ops.length; i >= 0; i -= 1) {
        stack.push(ops[i]);
    }
    pos = 0;
    balance = 0;
    i = 0;
    while (stack.length() !== 0) {
        op = stack.pop();
        if (op === '(') {
            balance -= 1;
            pos = i;
        } else if (op === ')') {
            balance += 1;
        }
        i += 1;
    }
    return balance < 0 ? pos : balance === 0 ? false : "too much ')'";
};

print(getPosition(expr1));
print(getPosition(expr2));
print(getPosition(expr3));

出力結果(Terminal, shell, SpiderMonkey)

$ js sample1.js
16
false
too much ')'
$

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