MonotonicArray896

Author: fluency03

src/MonotonicArray896.java

@@ -0,0 +1,64 @@
+/**
+ * An array is monotonic if it is either monotone increasing or monotone decreasing.
+ * 
+ * An array A is monotone increasing if for all i <= j, A[i] <= A[j].  An array A is
+ * monotone decreasing if for all i <= j, A[i] >= A[j].
+ * 
+ * Return true if and only if the given array A is monotonic.
+ * 
+ * Example 1:
+ * Input: [1,2,2,3]
+ * Output: true
+ * 
+ * Example 2:
+ * Input: [6,5,4,4]
+ * Output: true
+ * 
+ * Example 3:
+ * Input: [1,3,2]
+ * Output: false
+ * 
+ * Example 4:
+ * Input: [1,2,4,5]
+ * Output: true
+ * 
+ * Example 5:
+ * Input: [1,1,1]
+ * Output: true
+ * 
+ * Note:
+ * 1 <= A.length <= 50000
+ * -100000 <= A[i] <= 100000
+ */
+
+public class MonotonicArray896 {
+    public boolean isMonotonic(int[] A) {
+        if (A == null || A.length <= 2) return true;
+        int i = 1;
+        int len = A.length;
+        while (i < len && A[i] == A[i-1]) i++;
+        if (i == len) return true;
+        boolean flag = A[i] > A[i-1];
+        while (i < len) {
+            if (A[i] != A[i-1] && flag != A[i] > A[i-1]) return false;
+            i++;
+        }
+        return true;
+    }
+
+    /**
+     * https://leetcode.com/problems/monotonic-array/solution/
+     */
+    public boolean isMonotonic2(int[] A) {
+        int store = 0;
+        for (int i = 0; i < A.length - 1; ++i) {
+            int c = Integer.compare(A[i], A[i+1]);
+            if (c != 0) {
+                if (c != store && store != 0)
+                    return false;
+                store = c;
+            }
+        }
+        return true;
+    }
+}