Create 2999_Count_the_Number_of_Powerful_Intergers.java

Author: vishwajeetmishra4

JAVA/2999_Count_the_Number_of_Powerful_Intergers.java

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+// Problem Number: 2999
+
+// Count the Numbers of Powerful Integers.
+
+class Solution {
+    private String s;
+    private String a, b;
+    private int limit;
+    private Long[][][] memo;
+
+    public long numberOfPowerfulInt(long start, long finish, int limit, String s) {
+        this.s = s;
+        this.a = String.valueOf(start);
+        this.b = String.valueOf(finish);
+        this.limit = limit;
+
+        // Pad a and s with leading zeros to match the length of b
+        a = "0".repeat(b.length() - a.length()) + a;
+        s = "0".repeat(b.length() - s.length()) + s;
+
+        memo = new Long[b.length()][2][2];
+
+        return count(0, true, true);
+    }
+
+    private long count(int i, boolean tightA, boolean tightB) {
+        if (i + s.length() == b.length()) {
+            String aMinSuffix = tightA ? a.substring(b.length() - s.length()) : "0".repeat(s.length());
+            String bMaxSuffix = tightB ? b.substring(b.length() - s.length()) : "9".repeat(s.length());
+
+            long suffix = Long.parseLong(s);
+            long aMin = Long.parseLong(aMinSuffix);
+            long bMax = Long.parseLong(bMaxSuffix);
+
+            return (aMin <= suffix && suffix <= bMax) ? 1 : 0;
+        }
+
+        int tA = tightA ? 1 : 0;
+        int tB = tightB ? 1 : 0;
+        if (memo[i][tA][tB] != null) {
+            return memo[i][tA][tB];
+        }
+
+        long res = 0;
+        int minDigit = tightA ? a.charAt(i) - '0' : 0;
+        int maxDigit = tightB ? b.charAt(i) - '0' : 9;
+
+        for (int d = minDigit; d <= maxDigit; ++d) {
+            if (d > limit) continue;
+            boolean nextTightA = tightA && (d == minDigit);
+            boolean nextTightB = tightB && (d == maxDigit);
+            res += count(i + 1, nextTightA, nextTightB);
+        }
+
+        memo[i][tA][tB] = res;
+        return res;
+    }
+}