refactor 1150

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_1150.java

@@ -27,8 +27,25 @@
  **/
 public class _1150 {
     public static class Solution1 {
+        /**credit: https://leetcode.com/problems/check-if-a-number-is-majority-element-in-a-sorted-array/discuss/358130/Java-just-one-binary-search-O(logN))-0ms-beats-100*/
         public boolean isMajorityElement(int[] nums, int target) {
-            return nums[(nums.length - 1) / 2] == target;
+            int firstIndex = findFirstOccur(nums, target);
+            int plusHalfIndex = firstIndex + nums.length / 2;
+            return plusHalfIndex < nums.length && nums[plusHalfIndex] == target;
+        }
+
+        private int findFirstOccur(int[] nums, int target) {
+            int left = 0;
+            int right = nums.length;
+            while (left < right) {
+                int mid = left + (right - left) / 2;
+                if (nums[mid] < target) {
+                    left = mid + 1;
+                } else if (nums[mid] >= target) {
+                    right = mid;
+                }
+            }
+            return left;
         }
     }
 }

src/test/java/com/fishercoder/_1150Test.java

@@ -27,4 +27,10 @@ public void test2() {
         assertEquals(false, solution1.isMajorityElement(nums, 101));
     }
 
+    @Test
+    public void test3() {
+        nums = new int[]{1, 1, 1, 2, 3, 3, 3};
+        assertEquals(false, solution1.isMajorityElement(nums, 2));
+    }
+
 }