June22: smallest beautiful string [H]

Greedy, Time: O(N), Space: O(1): in-place update

daily/June21.cpp

@@ -9,8 +9,7 @@ class Solution {
    *
    * @param temperatureA
    * @param temperatureB
-   * @return int
-   */
+   * @return int */
   int temperatureTrend(vector<int>& temperatureA, vector<int>& temperatureB) {
     auto cmp = [](int x, int y) { return (x > y) - (x < y); };
 

daily/June22.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+ public:
+  /**
+   * @brief LC: 2663: Lexicographically Smallest Beautiful string
+   * Greedy algorithm
+   * Time: O(N), N: len(s), Space: O(1), inplace update
+   *
+   * @param s
+   * @param k
+   * @return string
+   */
+  string smallestBeautifulString(string s, int k) {
+    k += 'a';
+    int n = s.length();
+    int i = n - 1;  // start from last letter
+
+    s[i]++;
+    while (i < n) {
+      if (s[i] == k) {  // go upgrade
+        if (i == 0) {   // can't go upgrade
+          return "";
+        }
+        // go upgrade
+        s[i] = 'a';
+        s[--i]++;
+      } else if (i && s[i] == s[i - 1] || i > 1 && s[i] == s[i - 2]) {
+        s[i]++;  // if s[i] form the
+      } else {
+        i++;  // check the latter
+      }
+    }
+    return s;
+  }
+};