designANumberContainerSystem.js

var NumberContainers = function () {
  this.m = new Map();
  this.d = new Map();
};
NumberContainers.prototype.change = function (i, n) {
  if (this.m.has(i) && this.m.get(i) == n) return;
  this.m.set(i, n);
  if (!this.d.has(n)) this.d.set(n, new MinHeap());
  this.d.get(n).push(i);
};
NumberContainers.prototype.find = function (n) {
  if (!this.d.has(n)) return -1;
  let h = this.d.get(n);
  while (h.size() && this.m.get(h.peek()) !== n) h.pop();
  return h.size() ? h.peek() : -1;
};
function MinHeap() {
  this.a = [];
}
MinHeap.prototype.push = function (x) {
  this.a.push(x);
  let i = this.a.length - 1;
  while (i > 0) {
    let p = (i - 1) >> 1;
    if (this.a[p] <= this.a[i]) break;
    [this.a[p], this.a[i]] = [this.a[i], this.a[p]];
    i = p;
  }
};
MinHeap.prototype.pop = function () {
  let r = this.a[0],
    l = this.a.pop();
  if (this.a.length) {
    this.a[0] = l;
    let i = 0,
      n = this.a.length;
    while (true) {
      let l = i * 2 + 1,
        r = i * 2 + 2,
        m = i;
      if (l < n && this.a[l] < this.a[m]) m = l;
      if (r < n && this.a[r] < this.a[m]) m = r;
      if (m === i) break;
      [this.a[i], this.a[m]] = [this.a[m], this.a[i]];
      i = m;
    }
  }
  return r;
};
MinHeap.prototype.peek = function () {
  return this.a[0];
};
MinHeap.prototype.size = function () {
  return this.a.length;
};