[рони]

jsNotGuru,

function fn(c) {
    var d = {};
    return c.slice().sort(function(a, b) {
        return a - b
    }).map(function(a) {
        var b = d[a] || 0,
            b = c.indexOf(a, b);
        d[a] = b + 1;
        return b
    })
};
alert(fn([3, 1, 2]))
alert(fn([3, 3, 1, 2]))