Solved, yay I'm happy. I had to put this aside for a couple of monthsHEADmaster

due to busy work and family life. Yesterday and today I got a little
time so I fired up IDEA and started hacking at this again.

Lesson learned/reinforced: don't give up, don't dismiss small steps,
take those steps like a marathon, and you'll inch closer and finally
reach the destination! I found that it helped me that I wrote down
those little steps, started them, finished them, and closed them one
by one. This gave me momentum to carry it through! Pretty happy about
it.

2 files changed, 184 insertions, 19 deletions

diff --git a/src/main/SetRangeSum.java b/src/main/SetRangeSum.java
index 8c75189..0d01382 100644
--- a/src/main/SetRangeSum.java
+++ b/src/main/SetRangeSum.java
@@ -8,6 +8,7 @@ public class SetRangeSum {
     StringTokenizer st;
     boolean eof;
 
+    //    int last_sum_result = 0;
     long last_sum_result = 0;
     // Splay tree implementation
 
@@ -190,47 +191,57 @@ public class SetRangeSum {
     }
 
     void erase(int x) {
-        // Implement erase yourself
+        if (find(x)) {
+            root = merge(root.left, root.right);
+            if (root != null)
+                root.parent = null;
+            return;
+        }
+    }
+
+    boolean find(int x) {
+        if (root != null && root.key == x) return true;
         Vertex left = null;
         Vertex right = null;
-        Vertex new_vertex = null;
         VertexPair leftRight = split(root, x);
         left = leftRight.left;
         right = leftRight.right;
-
-        if (right == null) return;
-
-        new_vertex = right.right;
-        root = merge(left, new_vertex);
-
-    }
-
-    boolean find(int x) {
-        // Implement find yourself
-        VertexPair vertexPair = find(root, x);
-        if (vertexPair.left == null) return false;
-        if (vertexPair.left.key == x)
-            return true;
-        else return false;
+        if (right == null || right.key != x) {
+            root = merge(left, right);
+            if (right == null)
+                root = splay(left);
+            else
+                root = splay(right);
+            return false;
+        }
+        root = merge(left, right);
+        root = splay(right);
+        return true;
     }
 
     long sum(int from, int to) {
+        long ans = 0;
         VertexPair leftMiddle = split(root, from);
         Vertex left = leftMiddle.left;
         Vertex middle = leftMiddle.right;
         VertexPair middleRight = split(middle, to + 1);
         middle = middleRight.left;
         Vertex right = middleRight.right;
-        long ans = 0;
         if (left != null && left.key >= from && left.key <= to)
             ans = ans + left.sum;
+//        ans = ans + left.key;
+//        if (middle != null)
         if (middle != null && middle.key >= from && middle.key <= to)
             ans = ans + middle.sum;
         if (right != null && right.key >= from && right.key <= to)
             ans = ans + right.sum;
+//        ans = ans + right.key;
+        root = merge(merge(left, middle), right);
+//        last_sum_result = (int) (ans % MODULO);
         last_sum_result = ans;
 
         return ans;
+//        return last_sum_result;
     }
 
 
@@ -261,7 +272,7 @@ public class SetRangeSum {
                     int r = nextInt();
                     long res = sum((int) (l + last_sum_result) % MODULO, (int) (r + last_sum_result) % MODULO);
                     out.println(res);
-                    last_sum_result = (res % MODULO);
+                    last_sum_result = (int) (res % MODULO);
                 }
             }
         }
diff --git a/src/test/SetRangeSumTest.java b/src/test/SetRangeSumTest.java
new file mode 100644
index 0000000..60cd5df
--- /dev/null
+++ b/src/test/SetRangeSumTest.java
@@ -0,0 +1,154 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class SetRangeSumTest {
+    @Test
+    void test1() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        assertFalse(setRangeSum.find((int) ((1 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((1 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((1 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((2 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(3, setRangeSum.sum((int) (1 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (2 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((1000000000 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((1000000000 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((1000000000 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((1000000000 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(1, setRangeSum.sum((int) (999999999 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (1000000000 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((2 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((2 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((9 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(10, setRangeSum.sum((int) (0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (9 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+    }
+
+    @Test
+    void test2() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        assertFalse(setRangeSum.find((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+    }
+
+    @Test
+    void test3() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        setRangeSum.insert((int) ((491572259 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((491572259 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertFalse(setRangeSum.find((int) ((899375874 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(491572259, setRangeSum.sum((int) (310971296 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (877523306 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((352411209 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+    }
+
+    @Test
+    void testGraderCase5() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        assertEquals(0, setRangeSum.sum((int) (88127140 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (859949755 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (407584225 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (906606553 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((885530090 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((234423189 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(234423189, setRangeSum.sum((int) (30746291 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (664192454 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((465752492 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(934598870, setRangeSum.sum((int) (848498590 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (481606032 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+    }
+
+    @Test
+    void testAchievingBetterUnderstanding() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        setRangeSum.insert((int) ((7 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((7 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((7 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((7 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((3 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((3 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertTrue(setRangeSum.find((int) ((3 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(3, setRangeSum.sum((int) (3 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (3 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+    }
+
+    @Test
+    void testGraderCase20() {
+        SetRangeSum setRangeSum = new SetRangeSum();
+
+        assertEquals(0, setRangeSum.sum((int) (40279559 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (89162572 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((774613289 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (869592654 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (915517087 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((165280355 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((776346290 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((221187096 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (421986248 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (742826969 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (83228103 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (852190011 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((640319482 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((528689193 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertFalse(setRangeSum.find((int) ((75245219 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((617070033 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (25751289 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (70170547 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (28248247 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (617849094 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((954357244 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((477444954 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((608389416 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(0, setRangeSum.sum((int) (400483980 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (423330836 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((477444954 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((441393551 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(66257759, setRangeSum.sum((int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((822218158 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((806479414 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(0, setRangeSum.sum((int) (548665149 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (925635534 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((234121006 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((663305907 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(729563666, setRangeSum.sum((int) (314809050 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (685231317 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (487458874 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (602635501 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((918193520 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertFalse(setRangeSum.find((int) ((606474691 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(0, setRangeSum.sum((int) (188185089 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (774086933 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((322445571 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((814123984 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(66257759, setRangeSum.sum((int) (0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (0 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) (689260392 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (827869844 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((204276815 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((66257759 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((488766408 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(0, setRangeSum.sum((int) (412617563 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (631410280 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((463415495 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((601030115 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((776513589 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(601030115, setRangeSum.sum((int) (257003372 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (887483600 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((154047223 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertTrue(setRangeSum.find((int) ((154047223 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertFalse(setRangeSum.find((int) ((219327735 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((978812473 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(1935950040, setRangeSum.sum((int) (978812473 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (154047223 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((718062555 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertFalse(setRangeSum.find((int) ((128066784 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.erase((int) ((15718305 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((754978417 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(1935950040, setRangeSum.sum((int) ((643892549 + setRangeSum.last_sum_result) % SetRangeSum.MODULO), (int) ((819127300 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+//        assertEquals(1935950040, setRangeSum.sum((int) (643892549 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (819127300 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((192401474 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertTrue(setRangeSum.find((int) ((643892549 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((638898307 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertFalse(setRangeSum.find((int) ((973173529 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        setRangeSum.insert((int) ((506709268 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((506709268 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((744166533 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.erase((int) ((638898307 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        setRangeSum.insert((int) ((95240753 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+        assertEquals(0, setRangeSum.sum((int) ((997348833 + setRangeSum.last_sum_result) % SetRangeSum.MODULO), (int) ((63778002 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertTrue(setRangeSum.find((int) ((31190791 + setRangeSum.last_sum_result) % SetRangeSum.MODULO)));
+        assertEquals(31190791, setRangeSum.sum((int) (21011834 + setRangeSum.last_sum_result) % SetRangeSum.MODULO, (int) (570648768 + setRangeSum.last_sum_result) % SetRangeSum.MODULO));
+    }
+
+}