Added task 2180

Author: AryamanMishra

src/main/java/g2101_2200/s2180_count_integers_with_even_digit_sum/Solution.java

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+package g2101_2200.s2180_count_integers_with_even_digit_sum;
+
+// #Easy #Math #Simulation #2022_06_08_Time_0_ms_(100.00%)_Space_41.1_MB_(42.90%)
+
+public class Solution {
+ public int countEven(int n) {
+ if (n % 2 == 1) {
+ return n/2;
+ }
+ else {
+ int ans = 0;
+ int num = n;
+ while (num != 0) {
+ ans += num % 10;
+ num /= 10;
+ }
+ if (ans % 2 == 0) {
+ return n/2;
+ }
+ else {
+ return n/2 - 1;
+ }
+ }
+ }
+}

src/main/java/g2101_2200/s2180_count_integers_with_even_digit_sum/readme.md

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+2180\. Count Integers With Even Digit Sum
+
+Easy
+
+Given a positive integer `num`, return _the number of positive integers **less than or equal to**_ `num` _whose digit sums are **even**_.
+
+The **digit sum** of a positive integer is the sum of all its digits.
+
+**Example 1:**
+
+**Input:** num = 4
+
+**Output:** 2
+
+**Explanation:** The only integers less than or equal to 4 whose digit sums are even are 2 and 4.
+
+**Example 2:**
+
+**Input:** num = 30
+
+**Output:** 14
+
+**Explanation:** The 14 integers less than or equal to 30 whose digit sums are even are 2, 4, 6, 8, 11, 13, 15, 17, 19, 20, 22, 24, 26, and 28.
+
+**Constraints:**
+
+* `1 <= num <= 1000`

src/test/java/g2101_2200/s2180_count_integers_with_even_digit_sum/SolutionTest.java

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+package g2101_2200.s2180_count_integers_with_even_digit_sum;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void countEven() {
+ assertThat(new Solution().countEven(4), equalTo(2));
+ }
+
+ @Test
+ void countEven2() {
+ assertThat(new Solution().countEven(30), equalTo(14));
+ }
+}