java: add «27. Remove Element»

URL:	https://leetcode.com/problems/remove-element/

java/remove-element.java

@@ -0,0 +1,32 @@
+class Solution {
+  private static int skipVal(int[] nums, int val, int i) {
+    for (
+    /* no-op */ ; i >= 0 && nums[i] == val; /* no-op */ ) {
+      --i;
+    }
+
+    return i;
+  }
+
+  public int removeElement(int[] nums, int val) {
+    var r = skipVal(nums, val, nums.length - 1);
+
+    int l;
+    for (l = 0; l < r; ++l) {
+      if (nums[l] == val) {
+        var tmp = nums[l];
+        nums[l] = nums[r];
+        nums[r] = tmp;
+
+        r = skipVal(nums, val, r);
+      }
+    }
+
+    // shift ‹l› to the first ‹val›
+    while (l < nums.length && nums[l] != val) {
+      ++l;
+    }
+
+    return l;
+  }
+}