Create LC_lexsmalleststrafterop.java

src/test/java/LeetCode/Lexicographically_Smallest_String_After_Applying_Operations/LC_lexsmalleststrafterop.java

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+class LC_lexsmalleststrafterop {
+
+    public String findLexSmallestString(String s, int a, int b) {
+        int n = s.length();
+        boolean[] vis = new boolean[n];
+        String res = s;
+        // double the length of s for convenience in extracting the rotated string t
+        s = s + s;
+        for (int i = 0; !vis[i]; i = (i + b) % n) {
+            vis[i] = true;
+            for (int j = 0; j < 10; j++) {
+                int kLimit = b % 2 == 0 ? 0 : 9;
+                for (int k = 0; k <= kLimit; k++) {
+                    // before each accumulation, re-truncate t
+                    char[] t = s.substring(i, i + n).toCharArray();
+                    for (int p = 1; p < n; p += 2) {
+                        t[p] = (char) ('0' + ((t[p] - '0' + j * a) % 10));
+                    }
+                    for (int p = 0; p < n; p += 2) {
+                        t[p] = (char) ('0' + ((t[p] - '0' + k * a) % 10));
+                    }
+                    String tStr = new String(t);
+                    if (tStr.compareTo(res) < 0) {
+                        res = tStr;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}