From bfe3c82c399d20af2c42ff05b5e747bb6ec0e0fd Mon Sep 17 00:00:00 2001
From: Ben Makusha <btmakusha@duck.com>
Date: Sat, 15 Nov 2025 22:34:09 -0500
Subject: [PATCH] chore: [LEETCODE 1513] Number of Substrings With Only 1s <>
 Solution

---
 .../a1513/NumberOfSubstringsWithOnlyOnes.java | 19 ++++++++++
 .../NumberOfSubstringsWithOnlyOnesTest.java   | 38 +++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 src/main/java/problemset/a1513/NumberOfSubstringsWithOnlyOnes.java
 create mode 100644 src/test/java/problemset/a1513/NumberOfSubstringsWithOnlyOnesTest.java

diff --git a/src/main/java/problemset/a1513/NumberOfSubstringsWithOnlyOnes.java b/src/main/java/problemset/a1513/NumberOfSubstringsWithOnlyOnes.java
new file mode 100644
index 0000000..63d5682
--- /dev/null
+++ b/src/main/java/problemset/a1513/NumberOfSubstringsWithOnlyOnes.java
@@ -0,0 +1,19 @@
+package problemset.a1513;
+
+public class NumberOfSubstringsWithOnlyOnes {
+    final int MODULO = (int) 1e9 + 7;
+
+    public int numSub(String s) {
+        int res = 0, consecutiveOnes = 0;
+
+        for (char c : s.toCharArray()) {
+            if (c == '1')
+                consecutiveOnes++;
+            else
+                consecutiveOnes = 0;
+
+            res = (res + consecutiveOnes) % MODULO;
+        }
+        return res;
+    }
+}
diff --git a/src/test/java/problemset/a1513/NumberOfSubstringsWithOnlyOnesTest.java b/src/test/java/problemset/a1513/NumberOfSubstringsWithOnlyOnesTest.java
new file mode 100644
index 0000000..34b58f2
--- /dev/null
+++ b/src/test/java/problemset/a1513/NumberOfSubstringsWithOnlyOnesTest.java
@@ -0,0 +1,38 @@
+package problemset.a1513;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class NumberOfSubstringsWithOnlyOnesTest {
+    private NumberOfSubstringsWithOnlyOnes numSubstrings;
+
+    private String testcaseOne;
+    private String testcaseTwo;
+    private String testcaseThree;
+
+    @BeforeEach
+    void setUp() {
+        numSubstrings = new NumberOfSubstringsWithOnlyOnes();
+
+        testcaseOne = "0110111";
+        testcaseTwo = "101";
+        testcaseThree = "111111";
+    }
+
+    @Test
+    void test_numSub_testCaseOne() {
+        assertEquals(9, numSubstrings.numSub(testcaseOne));
+    }
+
+    @Test
+    void test_numSub_testCaseTwo() {
+        assertEquals(2, numSubstrings.numSub(testcaseTwo));
+    }
+
+    @Test
+    void test_numSub_testCaseThree() {
+        assertEquals(21, numSubstrings.numSub(testcaseThree));
+    }
+}
\ No newline at end of file