Create maximum-swap.cpp

C++/maximum-swap.cpp

@@ -0,0 +1,21 @@
+// Time:  O(l), l is the length of the number string
+// Space: O(l)
+
+class Solution {
+public:
+    int maximumSwap(int num) {
+        string digits = to_string(num);
+        int left = 0, right = 0;
+        int max_idx = digits.length() - 1;
+        for (int i = digits.length() - 1; i >= 0; --i) {
+            if (digits[i] > digits[max_idx]) {
+                max_idx = i;
+            } else if (digits[max_idx] > digits[i]) {
+                left = i;
+                right = max_idx;
+            }
+        }
+        swap(digits[left], digits[right]);
+        return stoi(digits);
+    }
+};