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feat: add solutions to lc problem: No.0852.Peak Index in a Mountain Array
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‎solution/0800-0899/0852.Peak Index in a Mountain Array/README.md

Lines changed: 66 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -75,22 +75,87 @@
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<!-- 这里可写通用的实现逻辑 -->
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二分查找
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def peakIndexInMountainArray(self, arr: List[int]) -> int:
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n = len(arr)
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left, right = 1, n - 2
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while left < right:
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mid = (left + right) // 2
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if arr[mid] < arr[mid + 1]:
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left = mid + 1
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else:
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right = mid
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return right
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int peakIndexInMountainArray(int[] arr) {
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int n = arr.length;
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int left = 1, right = n - 2;
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while (left < right) {
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int mid = left + (right - left) / 2;
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if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
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return right;
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}
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}
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```
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### **Go**
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```go
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func peakIndexInMountainArray(arr []int) int {
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n := len(arr)
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left, right := 1, n-2
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for left < right {
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mid := left + (right-left)/2
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if arr[mid] < arr[mid+1] {
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left = mid + 1
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} else {
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right = mid
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}
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}
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return right
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int peakIndexInMountainArray(vector<int>& arr) {
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int n = arr.size();
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int left = 1, right = n - 2;
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while (left < right) {
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int mid = left + (right - left) / 2;
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if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
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return right;
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}
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};
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```
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### **...**

‎solution/0800-0899/0852.Peak Index in a Mountain Array/README_EN.md

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Original file line numberDiff line numberDiff line change
@@ -49,18 +49,83 @@
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## Solutions
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binary search
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<!-- tabs:start -->
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### **Python3**
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```python
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class Solution:
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def peakIndexInMountainArray(self, arr: List[int]) -> int:
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n = len(arr)
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left, right = 1, n - 2
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while left < right:
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mid = (left + right) // 2
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if arr[mid] < arr[mid + 1]:
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left = mid + 1
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else:
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right = mid
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return right
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```
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### **Java**
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```java
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class Solution {
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public int peakIndexInMountainArray(int[] arr) {
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int n = arr.length;
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int left = 1, right = n - 2;
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while (left < right) {
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int mid = left + (right - left) / 2;
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if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
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return right;
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}
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}
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```
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### **Go**
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```go
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func peakIndexInMountainArray(arr []int) int {
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n := len(arr)
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left, right := 1, n-2
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for left < right {
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mid := left + (right-left)/2
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if arr[mid] < arr[mid+1] {
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left = mid + 1
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} else {
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right = mid
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}
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}
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return right
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int peakIndexInMountainArray(vector<int>& arr) {
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int n = arr.size();
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int left = 1, right = n - 2;
118+
while (left < right) {
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int mid = left + (right - left) / 2;
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if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
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return right;
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}
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};
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```
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### **...**

‎solution/0800-0899/0852.Peak Index in a Mountain Array/Solution.cpp

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
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class Solution {
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public:
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int peakIndexInMountainArray(vector<int>& arr) {
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int n = arr.size();
5+
int left = 1, right = n - 2;
6+
while (left < right) {
7+
int mid = left + (right - left) / 2;
8+
if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
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return right;
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}
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};

‎solution/0800-0899/0852.Peak Index in a Mountain Array/Solution.go

Lines changed: 13 additions & 0 deletions
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@@ -0,0 +1,13 @@
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func peakIndexInMountainArray(arr []int) int {
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n := len(arr)
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left, right := 1, n-2
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for left < right {
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mid := left + (right-left)/2
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if arr[mid] < arr[mid+1] {
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left = mid + 1
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} else {
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right = mid
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}
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}
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return right
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}

‎solution/0800-0899/0852.Peak Index in a Mountain Array/Solution.java

Lines changed: 11 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,15 @@
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class Solution {
2-
public int peakIndexInMountainArray(int[] A) {
3-
int l = 0, r = A.length - 1;
4-
while (l < r) {
5-
int mid = l + r >>> 1;
6-
if (A[mid] > A[mid + 1]) r = mid;
7-
else l = mid + 1;
2+
public int peakIndexInMountainArray(int[] arr) {
3+
int n = arr.length;
4+
int left = 1, right = n - 2;
5+
while (left < right) {
6+
int mid = left + (right - left) / 2;
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if (arr[mid] < arr[mid + 1]) {
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left = mid + 1;
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} else {
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right = mid;
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}
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}
9-
return r;
13+
return right;
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}
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}

‎solution/0800-0899/0852.Peak Index in a Mountain Array/Solution.py

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
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class Solution:
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def peakIndexInMountainArray(self, arr: List[int]) -> int:
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n = len(arr)
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left, right = 1, n - 2
5+
while left < right:
6+
mid = (left + right) // 2
7+
if arr[mid] < arr[mid + 1]:
8+
left = mid + 1
9+
else:
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right = mid
11+
return right

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