feat: add the solution of Largest Number At Least Twice of Others(747) with Java.

Author: Mukyu

README.md

@@ -86,7 +86,7 @@
 | [733][733-question] | [Flood Fill][733-tips]                                       | [✅][733-java] | [✅][733-js] |                  |
 | [744][744-question] | [Find Smallest Letter Greater Than Target][744-tips]         | [✅][744-java] | [✅][744-js] |                  |
 | [746][746-question] | [Min Cost Climbing Stairs][746-tips]                         | [✅][746-java] | [✅][746-js] |                  |
-| [747][747-question] | [Largest Number At Least Twice of Others][747-tips]          |                | [✅][747-js] |                  |
+| [747][747-question] | [Largest Number At Least Twice of Others][747-tips]          | [✅][747-java] | [✅][747-js] |                  |
 | [762][762-question] | [Prime Number of Set Bits in Binary Representation][762-tips]|                | [✅][762-js] |                  |
 | [766][766-question] | [Toeplitz Matrix][766-tips]                                  |                | [✅][766-js] |                  |
 | [771][771-question] | [Jewels and Stones][771-tips]                                | [✅][771-java] | [✅][771-js] | [✅][771-kotlin] |
@@ -484,6 +484,7 @@
 [733-java]: ./src/_733/Solution.java
 [744-java]: ./src/_744/Solution.java
 [746-java]: ./src/_746/Solution.java
+[747-java]: ./src/_747/Solution.java
 [771-java]: ./src/_771/Solution.java
 [804-java]: ./src/_804/Solution.java
 

src/_747/Solution.java

@@ -0,0 +1,26 @@
+package _747;
+
+class Solution {
+    public int dominantIndex(int[] nums) {
+        int max = 0;
+        int index = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] > max) {
+                max = nums[i];
+                index = i;
+            }
+        }
+        for (int num : nums) {
+            if (num < max && max < num + num) {
+                return -1;
+            }
+        }
+        return index;
+    }
+
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.dominantIndex(new int[] {3, 6, 1, 0}));
+        System.out.println(solution.dominantIndex(new int[] {1, 2, 3, 4}));
+    }
+}

tips/747/README.md

@@ -1,46 +1,66 @@
-[xxxx][title]
+[Largest Number At Least Twice of Others][title]
 
 ## Description
-// 抄题目
 
+In a given integer array `nums`, there is always exactly one largest element.
 
-**Example:**
+Find whether the largest element in the array is at least twice as much as every other number in the array.
+
+If it is, return the **index** of the largest element, otherwise return -1.
+
+**Example 1:**
 
 ```
-// 抄Example
+Input: nums = [3, 6, 1, 0]
+Output: 1
+Explanation: 6 is the largest integer, and for every other number in the array x,
+6 is more than twice as big as x.  The index of value 6 is 1, so we return 1.
 ```
 
-**Note:**
-// Note
+**Example 2:**
 
-**Tags:** // tags
+```
+Input: nums = [1, 2, 3, 4]
+Output: -1
+Explanation: 4 isn't at least as big as twice the value of 3, so we return -1.
+```
 
+**Note:**
 
-## 思路 1
-// 贴一些关键代码,说一些解题思路
-// (同一种语言可以写多种思路，与某种语言思路相同的另一种语言的思路无须赘述，但可以把代码贴在后面) 
-```java
+1. `nums` will have a length in the range `[1, 50]`.
+2. Every `nums[i]` will be an integer in the range `[0, 99]`.
 
-```
-```javascript
+**Tags:** [Array](https://leetcode.com/tag/array/)
 
-```
+## 思路
 
-## 思路 2
-// 贴一些关键代码,说一些解题思路
-```java
+给出一个数组，此数组必定有一个最大值。要求判断此最大值是否是其他数的至少两倍大。
 
-```
+遍历找出最大值，再遍历进行比较即可。
 
-## 思路 3
-// 贴一些关键代码,说一些解题思路
-```kotlin
+**Java:**
 
+```
+public int dominantIndex(int[] nums) {
+    int max = 0;
+    int second = 0;
+    int index = 0;
+    for (int i = 0; i < nums.length; i++) {
+        if (nums[i] > max) {
+            second = max;
+            max = nums[i];
+            index = i;
+        } else if (nums[i] > second) {
+            second = nums[i];
+        }
+    }
+    return max >= second + second ? index : -1;
+}
 ```
 
 ## 结语
-   
+
 如果你同我们一样热爱数据结构、算法、LeetCode，可以关注我们 GitHub 上的 LeetCode 题解：[LeetCode-Solution][ls]
 
-[title]: https://leetcode.com/problems/xxxx
+[title]: https://leetcode.com/problems/largest-number-at-least-twice-of-others/description/
 [ls]: https://github.com/RichCodersAndMe/LeetCode-Solution