Added task 3756

src/main/java/g3701_3800/s3756_concatenate_non_zero_digits_and_multiply_by_sum_ii/Solution.java

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+package g3701_3800.s3756_concatenate_non_zero_digits_and_multiply_by_sum_ii;
+
+// #Medium #String #Math #Prefix_Sum #Weekly_Contest_477 #Staff
+// #2026_04_25_Time_14_ms_(100.00%)_Space_131.16_MB_(32.94%)
+
+public class Solution {
+    private static final long MOD = 1_000_000_007;
+
+    public int[] sumAndMultiply(String s, int[][] queries) {
+        int m = s.length();
+        long[] p = new long[m + 1];
+        long[] sum = new long[m + 1];
+        int[] cnt = new int[m + 1];
+        long[] pow10 = new long[m + 1];
+        pow10[0] = 1;
+        for (int i = 0; i < m; i++) {
+            int d = s.charAt(i) - '0';
+            if (d != 0) {
+                p[i + 1] = (p[i] * 10 + d) % MOD;
+            } else {
+                p[i + 1] = p[i];
+            }
+            sum[i + 1] = sum[i] + d;
+            cnt[i + 1] = cnt[i] + (d != 0 ? 1 : 0);
+            pow10[i + 1] = pow10[i] * 10 % MOD;
+        }
+        int[] ans = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int l = queries[i][0];
+            int r = queries[i][1];
+            int k = cnt[r + 1] - cnt[l];
+            long x = (p[r + 1] - p[l] * pow10[k] % MOD + MOD) % MOD;
+            long digitSum = sum[r + 1] - sum[l];
+            ans[i] = (int) (x * digitSum % MOD);
+        }
+        return ans;
+    }
+}

src/main/java/g3701_3800/s3756_concatenate_non_zero_digits_and_multiply_by_sum_ii/readme.md

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+3756\.

src/test/java/g3701_3800/s3756_concatenate_non_zero_digits_and_multiply_by_sum_ii/SolutionTest.java

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+package g3701_3800.s3756_concatenate_non_zero_digits_and_multiply_by_sum_ii;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+    @Test
+    void sumAndMultiply() {
+        assertThat(
+                new Solution().sumAndMultiply("10203004", new int[][] {{0, 7}, {1, 3}, {4, 6}}),
+                equalTo(new int[] {12340, 4, 9}));
+    }
+
+    @Test
+    void sumAndMultiply2() {
+        assertThat(
+                new Solution().sumAndMultiply("1000", new int[][] {{0, 3}, {1, 1}}),
+                equalTo(new int[] {1, 0}));
+    }
+
+    @Test
+    void sumAndMultiply3() {
+        assertThat(
+                new Solution().sumAndMultiply("9876543210", new int[][] {{0, 9}}),
+                equalTo(new int[] {444444137}));
+    }
+}