Leetcode

# 852. Peak Index in a Mountain Array

by hooni posted Apr 28, 2020
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Let's call an array `A` a mountain if the following properties hold:

• `A.length >= 3`
• There exists some `0 < i < A.length - 1` such that `A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1]`

Given an array that is definitely a mountain, return any `i` such that `A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1]`.

Example 1:

```Input: [0,1,0]
Output: 1
```

Example 2:

```Input: [0,2,1,0]
Output: 1```

Note:

1. `3 <= A.length <= 10000`
2. `0 <= A[i] <= 10^6`
3. A is a mountain, as defined above.

```/*
//가장 높은 점이 몇개인지 찾으라고 잘못 이해하고 만든..
class Solution {
public int peakIndexInMountainArray(int[] A) {
int max = -1;
Map<Integer, Integer> hmap = new HashMap<>();

for(int i=0; i<A.length; i++){
if(max < A[i]){
max = A[i];
hmap.put(max, hmap.getOrDefault(A[i],0)+1);
}
}

return hmap.get(max);
}
}
*/
//가장 높은 곳까지 올라가는 횟수
class Solution {
public int peakIndexInMountainArray(int[] A) {
int count = 0;
for(int i=0; i<A.length-1; i++){
if(A[i] < A[i+1]){
count++;
}
}

return count;
}
}```

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