[N-0] add 738

Author: fishercoder1534

README.md

@@ -23,6 +23,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
 |739|[Daily Temperatures](https://leetcode.com/problems/daily-temperatures/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_739.java) | O(n^2) | O(1) | Medium| 
+|738|[Monotone Increasing Digits](https://leetcode.com/problems/monotone-increasing-digits/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_738.java) | O(n) | O(1) | Medium|
 |737|[Sentence Similarity II](https://leetcode.com/problems/sentence-similarity-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_737.java) | O(nlogk + k) n is the length of max(words1, words2), k is the length of pairs| O(k) | Medium| Union Find
 |735|[Asteroid Collision](https://leetcode.com/problems/asteroid-collision/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_735.java) | O(n) | O(n) | Medium | Stack
 |734|[Sentence Similarity](https://leetcode.com/problems/sentence-similarity/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_734.java) | O(n*k) | O(1) | Easy | HashTable

src/main/java/com/fishercoder/solutions/_738.java

@@ -0,0 +1,39 @@
+package com.fishercoder.solutions;
+
+/**
+ * 738. Monotone Increasing Digits
+ *
+ * Given a non-negative integer N, find the largest number that is less than or equal to N with monotone increasing digits.
+ * (Recall that an integer has monotone increasing digits if and only if each pair of adjacent digits x and y satisfy x <= y.)
+
+ Example 1:
+ Input: N = 10
+ Output: 9
+
+ Example 2:
+ Input: N = 1234
+ Output: 1234
+
+ Example 3:
+ Input: N = 332
+ Output: 299
+
+ Note: N is an integer in the range [0, 10^9].
+ */
+public class _738 {
+    public static class Solution1 {
+        /**
+         * credit: https://discuss.leetcode.com/topic/112808/simple-python-solution-w-explanation/2
+         */
+        public int monotoneIncreasingDigits(int N) {
+            String s = Integer.toString(N);
+            int index = -1;
+            for (int i = s.length() - 2; i >= 0; i--) {
+                if (s.charAt(i) > s.charAt(i + 1) || (index != -1 && s.charAt(index) == s.charAt(i))) {
+                    index = i;
+                }
+            }
+            return index == -1 ? N : N - Integer.parseInt(s.substring(index + 1, s.length())) - 1;
+        }
+    }
+}

src/test/java/com/fishercoder/_738Test.java

@@ -0,0 +1,22 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._738;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class _738Test {
+    private static _738.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _738.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(9, solution1.monotoneIncreasingDigits(10));
+    }
+
+}