Missing file.

lectures/sorting/partition.java

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+/** Partition array {@code a} into {@code a[l..k)} and {@code a[k..r)},
+ * where {@code l < k < r}, and all elements in {@code a[l..k)} are
+ * less than or equal to all elements in {@code a[k..r)}.
+ * Requires: {@code 0≤l}, {@code r≤a.length}, and {@code r-l≥2}.
+ */
+int partition(int[] a, int l, int r) {
+    swap(a, l, l + random.nextInt(r-l));
+    int p = a[l];
+    int i = l, j = r - 1;
+    while (a[j] > p) j--;
+    while (i < j) {
+        swap(a, i, j); // swap a[i] and a[j]
+        do i++; while (a[i] < p);
+        do j--; while (a[j] > p);
+    }
+    return j+1;
+}
+