Create 3697-compute-decimal-representation.java

Author: sanajitjana

Easy/3697-compute-decimal-representation.java

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+/**
+ * Link: https://leetcode.com/problems/compute-decimal-representation/
+ * Title: Compute Decimal Representation
+ *
+ * Question:
+ * You are given an integer n. Your task is to break it down into its decimal components.
+ * For example:
+ *   n = 4321 → [4000, 300, 20, 1]
+ *   n = 5030 → [5000, 30]
+ *   n = 7    → [7]
+ *
+ * Return the decimal representation as an array of integers, excluding zeros.
+ *
+ * --------------------------------------------------------------------
+ * Approach:
+ * - Start with place value = 1 (units place).
+ * - While n > 0:
+ *      - Extract the last digit (digit = n % 10).
+ *      - If digit != 0, compute digit * place and store it.
+ *      - Update n by dividing it by 10.
+ *      - Update place by multiplying it by 10.
+ * - Reverse the list since we collect from lowest place to highest.
+ * - Convert the list into an integer array and return.
+ *
+ * --------------------------------------------------------------------
+ * Dry Run:
+ * n = 5030
+ * place = 1
+ * digit = 0 → skip
+ * n = 503, place = 10
+ * digit = 3 → add 30
+ * n = 50, place = 100
+ * digit = 0 → skip
+ * n = 5, place = 1000
+ * digit = 5 → add 5000
+ * Result list = [30, 5000]
+ * Reverse → [5000, 30]
+ * Output = [5000, 30]
+ *
+ * --------------------------------------------------------------------
+ * Time Complexity: O(log10(n)) 
+ *   - We process each digit once.
+ * Space Complexity: O(log10(n))
+ *   - We store at most one value per digit.
+ */
+
+class Solution {
+    public int[] decimalRepresentation(int n) {
+        List<Integer> base = new ArrayList<>();
+        int place = 1;
+        while (n > 0) {
+            int digit = n % 10;
+            if (digit != 0) {
+                base.add(digit * place);
+            }
+            n /= 10;
+            place *= 10;
+        }
+        Collections.reverse(base);
+        int[] list = new int[base.size()];
+        for (int i = 0; i < base.size(); i++) {
+            list[i] = base.get(i);
+        }
+        return list;
+    }
+}