fd

Author: dingjikerbo

solution/src/main/java/com/inuker/solution/FindPeakElement.java

@@ -8,23 +8,24 @@
  * https://leetcode.com/articles/find-peak-element/
  */
 public class FindPeakElement {
-
+    /**
+     * 首先局部峰值有很多
+     * 1，如果nums[mid]>nums[mid+1]，说明当前递减，左边肯定有个峰值，因为如果
+     * 没有，则意味着往左走会不停地上升，走到头的时候因为是负无穷，所以也相当于峰值
+     * 右边不一定有峰值，因为可能一直是下降趋势
+     * 2，如果nums[mid]<nums[mid+1]，说明当前是上升趋势，右边肯定有个峰值，理由同上
+     * 3，题目说了不存在nums[i]=nums[i+1]的情况
+     */
     public int findPeakElement(int[] nums) {
-        return Helper(nums, 0, nums.length - 1);
-    }
-
-    private int Helper(int[] nums, int low, int high) {
-        if (low == high) {
-            return low;
-        } else {
-            int mid1 = (low + high) / 2;
-            int mid2 = mid1 + 1;
-            if (nums[mid1] > nums[mid2]) {
-                return Helper(nums, low, mid1);
-            } else {
-                return Helper(nums, mid2, high);
-            }
+        int l = 0, r = nums.length - 1;
+        while (l < r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] > nums[mid + 1])
+                r = mid;
+            else
+                l = mid + 1;
         }
+        return l;
     }
 }
 

solution/src/main/java/com/inuker/solution/MissingNumber.java

@@ -7,11 +7,10 @@
 public class MissingNumber {
 
     public int missingNumber(int[] nums) {
-        int xor = 0, i = 0;
-        for (i = 0; i < nums.length; i++) {
-            xor = xor ^ i ^ nums[i];
+        int xor = nums.length;
+        for (int i = 0; i < nums.length; i++) {
+            xor ^= i ^ nums[i];
         }
-
-        return xor ^ i;
+        return xor;
     }
 }

test/src/main/java/com/inuker/test/main.java

@@ -31,10 +31,6 @@ public static void main(String[] args) {
         int[] arr = new int[] {
                 0, 0, 3, 4, 5, 0, 0
         };
-        new Test2().moveZeroes(arr);
-        for (int n : arr) {
-            System.out.print(n + " ");
-        }
     }
 
 }