#2283: Check if Number Has Equal Digit Count and Digit Value; solution & tests.

Author: vetalapo

c-sharp/Problems/arrays-and-hashing/CheckIfNumberHasEqualDigitCountAndDigitValue.cs

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+/**
+ * 2283
+ * Check if Number Has Equal Digit Count and Digit Value
+ **
+ * You are given a 0-indexed string num of length n consisting of digits.
+ *
+ * Return true if for every index i in the range 0 <= i < n,
+ * the digit i occurs num[i] times in num, otherwise return false.
+ *
+ * Example 1:
+ *   Input: num = "1210"
+ *   Output: true
+ *   Explanation:
+ *     num[0] = '1'. The digit 0 occurs once in num.
+ *     num[1] = '2'. The digit 1 occurs twice in num.
+ *     num[2] = '1'. The digit 2 occurs once in num.
+ *     num[3] = '0'. The digit 3 occurs zero times in num.
+ *     The condition holds true for every index in "1210", so return true.
+ *
+ * Example 2:
+ *   Input: num = "030"
+ *   Output: false
+ *   Explanation:
+ *     num[0] = '0'. The digit 0 should occur zero times, but actually occurs twice in num.
+ *     num[1] = '3'. The digit 1 should occur three times, but actually occurs zero times in num.
+ *     num[2] = '0'. The digit 2 occurs zero times in num.
+ *     The indices 0 and 1 both violate the condition, so return false.
+ *
+ * Constraints:
+ *   • n == num.length
+ *   • 1 <= n <= 10
+ *   • num consists of digits.
+ *
+ * Hint 1:
+ *   Count the frequency of each digit in num.
+ **
+ * https://leetcode.com/problems/check-if-number-has-equal-digit-count-and-digit-value/
+***/
+
+namespace Problems;
+
+public class CheckIfNumberHasEqualDigitCountAndDigitValue
+{
+    public bool DigitCount( string num )
+    {
+        int[] countMap = new int[10];
+
+        foreach ( char c in num )
+        {
+            countMap[c - '0']++;
+        }
+
+        for ( int i = 0; i < num.Length; i++ )
+        {
+            if ( countMap[i] != num[i] - '0' )
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}

c-sharp/Tests/arrays-and-hashing/CheckIfNumberHasEqualDigitCountAndDigitValueTests.cs

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+using NUnit.Framework;
+
+using Problems;
+
+public class CheckIfNumberHasEqualDigitCountAndDigitValueTests
+{
+    [TestCase( "1210", ExpectedResult = true )]
+    [TestCase( "030", ExpectedResult = false )]
+    public bool DigitCountTest( string num ) =>
+        new CheckIfNumberHasEqualDigitCountAndDigitValue().DigitCount( num );
+}