Mon 21 Jul 22:43:21 CEST 2025

js/x11/win/quickselect.js

@@ -0,0 +1,58 @@
+'use strict';
+
+module.exports = quickselect;
+module.exports.default = quickselect;
+
+function quickselect(arr, k, left, right, compare) {
+    quickselectStep(arr, k, left || 0, right || (arr.length - 1), compare || defaultCompare);
+};
+
+function quickselectStep(arr, k, left, right, compare) {
+
+    while (right > left) {
+        if (right - left > 600) {
+            var n = right - left + 1;
+            var m = k - left + 1;
+            var z = Math.log(n);
+            var s = 0.5 * Math.exp(2 * z / 3);
+            var sd = 0.5 * Math.sqrt(z * s * (n - s) / n) * (m - n / 2 < 0 ? -1 : 1);
+            var newLeft = Math.max(left, Math.floor(k - m * s / n + sd));
+            var newRight = Math.min(right, Math.floor(k + (n - m) * s / n + sd));
+            quickselectStep(arr, k, newLeft, newRight, compare);
+        }
+
+        var t = arr[k];
+        var i = left;
+        var j = right;
+
+        swap(arr, left, k);
+        if (compare(arr[right], t) > 0) swap(arr, left, right);
+
+        while (i < j) {
+            swap(arr, i, j);
+            i++;
+            j--;
+            while (compare(arr[i], t) < 0) i++;
+            while (compare(arr[j], t) > 0) j--;
+        }
+
+        if (compare(arr[left], t) === 0) swap(arr, left, j);
+        else {
+            j++;
+            swap(arr, j, right);
+        }
+
+        if (j <= k) left = j + 1;
+        if (k <= j) right = j - 1;
+    }
+}
+
+function swap(arr, i, j) {
+    var tmp = arr[i];
+    arr[i] = arr[j];
+    arr[j] = tmp;
+}
+
+function defaultCompare(a, b) {
+    return a < b ? -1 : a > b ? 1 : 0;
+}