20250615 finished.

src/problems/1432-max-difference-you-can-get-from-changing-an-integer.cpp

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+/**
+* [1432] Max Difference You Can Get From Changing an Integer
+ */
+#include <bits/stdc++.h>
+#include <gtest/gtest.h>
+using namespace std;
+
+
+// submission codes start here
+
+class Solution
+{
+public:
+    int maxDiff(int num)
+    {
+        string numString = to_string(num);
+
+        // Select the first, not 9 number.
+        int targetPos = 0;
+        while (targetPos < numString.size() - 1)
+        {
+            if (numString[targetPos] != '9')
+            {
+                break;
+            }
+
+            targetPos += 1;
+        }
+
+        auto maxNumber = replaceDigit(numString, numString[targetPos], '9');
+
+        targetPos        = 0;
+        char minimumChar = '1';
+        // If the first number is not 1, select the first number.
+        // If the first number is 1, select next, not zero number.
+        if (numString[targetPos] == '1')
+        {
+            targetPos   = 1;
+            minimumChar = '0';
+            while (targetPos < numString.size())
+            {
+                if (numString[targetPos] == '1')
+                {
+                    // Can not replace 1 when the first number is 1.
+                    targetPos += 1;
+                    continue;
+                }
+
+                if (numString[targetPos] != '0')
+                {
+                    break;
+                }
+
+                targetPos += 1;
+            }
+        }
+
+        int minNumber = num;
+        if (targetPos != numString.size())
+        {
+            minNumber = replaceDigit(numString, numString[targetPos], minimumChar);
+        }
+
+        return maxNumber - minNumber;
+    }
+
+    static auto replaceDigit(const string &num, char source, char target) -> int
+    {
+        int result = 0;
+        for (const char i : num)
+        {
+            if (i == source)
+            {
+                result = result * 10 + target - '0';
+            }
+            else
+            {
+                result = result * 10 + i - '0';
+            }
+        }
+
+        return result;
+    }
+};
+
+// submission codes end
+
+TEST(P1432, Test1)
+{
+    ASSERT_EQ(888, Solution().maxDiff(555));
+    ASSERT_EQ(8, Solution().maxDiff(9));
+    ASSERT_EQ(888, Solution().maxDiff(111));
+    ASSERT_EQ(80000, Solution().maxDiff(10000));
+}