Create 1796-second-largest-digit-in-a-string.java

Author: sanajitjana

Easy/1796-second-largest-digit-in-a-string.java

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+/**
+ * Problem: 1796. Second Largest Digit in a String
+ * Difficulty: Easy
+ * URL: https://leetcode.com/problems/second-largest-digit-in-a-string/
+ * 
+ * Approach:
+ * - Track the maximum and second maximum digits found while iterating.
+ * - Update second maximum when a new maximum appears or when finding a digit between them.
+ * 
+ * Time Complexity: O(n)  // scan string once
+ * Space Complexity: O(1) // only a few integer variables
+ */
+
+class Solution {
+    public int secondHighest(String s) {
+        int max = -1;
+        int sMax = -1;
+
+        for (char ch : s.toCharArray()) {
+            if (Character.isDigit(ch)) {
+                int num = ch - '0';
+                if (num > max) {
+                    sMax = max;
+                    max = num;
+                } else if (num < max && num > sMax) {
+                    sMax = num;
+                }
+            }
+        }
+        return sMax;
+    }
+}