JSFiddle - React, Tailwind, and code Playground
JavaScript
var DIMS = 16;
var BITS = 1;
var MASK = (Math.pow(2, BITS) - 1)|0;
var SIZE = DIMS * BITS;
var list = [];
var tree = null;
//
// set bit count (population count)
function popCnt(x) {
x = x - ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x + (x >> 8);
x = x + (x >> 16);
return x & 0x0000003F;
}
//
// manhattan distance
function dist(a, b) {
if(BITS == 1) {
return popCnt(a ^ b);
}
var result = 0;
for(var i=0; i<DIMS; i++) {
var shr = i * BITS;
result += Math.abs(((a >> shr) & MASK) - ((b >> shr) & MASK));
}
return result;
}
//
// Vantage point tree
// max size of tree leaf nodes
VP_LEAF_SIZE = 32;
// need to choose a reasonable maximum distance
VP_DISTANCE = (BITS === 1) ? SIZE : 32;
function VPTree(data) {
this.radius = null;
this.center = null;
this.values = null;
this.inside = null;
this.outside = null;
//
var n = data.length;
var r = data[0];
// leaf node?
if(n <= VP_LEAF_SIZE || n <= 1) {
this.values = [].concat(data);
return this;
}
this.center = r;
// process data for counts at all possible distances
var buckets = Array(VP_DISTANCE + 1);
for(var i=0; i<=VP_DISTANCE; i++) {
buckets[i] = 0;
}
// distance counts
for(var i=0; i<n; i++) {
var v = data[i];
var d = dist(r, v);
if(d < VP_DISTANCE) {
buckets[d]++;
} else {
buckets[VP_DISTANCE]++;
}
}
// distance offsets
var sum = 0;
for(var i=0; i<=VP_DISTANCE; i++) {
buckets[i] = (sum += buckets[i]);
}
// pivot index
var median = n >> 1;
var pivot = 1;
for(var i=1; i<=VP_DISTANCE; i++) {
if(buckets[i] > median) {
pivot = (i > 1 && median - buckets[i - 1] <= buckets[i] - median) ? i - 1 : i;
break;
}
}
this.radius = pivot;
// parition data...