public int FindDecreaseArray(int target, MountainArray mountainArr, int left, int right)
{
while (left < right)
{
var mid = (left + right) / 2;
var val = mountainArr.Get(mid);
if (val == target)
{
return(mid);
}
else if (val > target)
{
left = mid + 1;
}
else
{
right = mid;
}
}
if (mountainArr.Get(left) == target)
{
return(left);
}
return(-1);
}
public int FindInMountainArray(int target, MountainArray A)
{
int n = A.Length(), l = 0, r = n - 1, m, peak = 0;
// If I want find the index, I always use while (left < right)
// If I may return the index during the search, I'll use while (left <= right)
// find index of peak
while (peak < r)
{
m = (peak + r) / 2;
if (A.Get(m) < A.Get(m + 1))
{
peak = m + 1;
}
else
{
r = m;
}
}
// find target in the left of peak
int i = BinarySearch(A, target, 0, peak, true);
// find target in the right of peak
return(i != -1 ? i : BinarySearch(A, target, peak + 1, A.Length() - 1, false));
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int left = 0;
int right = mountainArr.Length() - 1;
// 先找到峰顶
while (left < right)
{
int mid = left + (right - left) / 2;
if (mountainArr.Get(mid) <= mountainArr.Get(mid + 1))
{
left = mid + 1;
}
else
{
right = mid;
}
}
// 根据题意，峰顶一定存在故不用判断。
int top = left;
int index = findInMountainArrayleft(0, top, target, mountainArr);
if (index == -1)
{
index = findInMountainArrayright(top, mountainArr.Length() - 1, target, mountainArr);
}
return(index);
}
// 执行用时: 124 ms, 在所有 C# 提交中击败了 25.00% 的用户
// 内存消耗: 25.1 MB, 在所有 C# 提交中击败了 100.00% 的用户
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int start = 0;
int end = mountainArr.Length() - 1;
while (start < end)
{
// Use this approach instead of (start + end) / 2 to avoid overflow.
int middle = start + (end - start) / 2;
if (mountainArr.Get(middle) < mountainArr.Get(middle + 1))
{
start = middle + 1;
}
else
{
end = middle - 1;
}
}
int peak = start;
Console.WriteLine($"peak = {peak}");
int indexOfTarget = this.BinarySearchMountainArray(mountainArr, target, 0, peak);
if (indexOfTarget != -1)
{
return(indexOfTarget);
}
return(this.BinarySearchMountainArray(mountainArr, target, peak + 1, mountainArr.Length() - 1, false));
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int length = mountainArr.Length();
int left = 0;
int right = length - 1;
while (left <= right)
{
var mid = left + (right - left) / 2;
if (mountainArr.Get(mid) < mountainArr.Get(mid + 1))
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
var peak = left;
var index = BinarySearch(target, mountainArr, 0, peak, true);
if (index < 0)
{
index = BinarySearch(target, mountainArr, peak + 1, length - 1, false);
}
return(index);
}
private int findInMountainArrayright(int left, int right, int target, MountainArray mountainArr)
{
while (left < right)
{
int mid = left + (right - left) / 2;
int midNum = mountainArr.Get(mid);
if (midNum > target)
{
left = mid + 1;
}
else if (midNum < target)
{
right = mid;
}
else if (midNum == target)
{
return(mid);
}
}
// 区间缩小为一个元素时单独判断
if (mountainArr.Get(left) == target)
{
return(left);
}
return(-1);
}
public int FindPeak(MountainArray arr)
{
int l = 0;
int r = n - 1;
while (l <= r)
{
int mid = l + (r - l) / 2;
if (mid - 1 < 0 || arr.Get(mid) > arr.Get(mid - 1))
{
if (mid + 1 >= n || arr.Get(mid) > arr.Get(mid + 1))
{
return(mid);
}
else
{
l = mid + 1;
}
}
else
{
r = mid - 1;
}
}
return(-1);
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int left = 0;
int right = mountainArr.Length() - 1;
while (left < right)
{
int mid = left + (right - left) / 2;
if (mountainArr.Get(mid) < mountainArr.Get(mid + 1))
{
left = mid + 1;
}
else
{
right = mid;
}
}
int index = BinarySearch(target, mountainArr, 0, right, true);
if (index == -1)
{
index = BinarySearch(target, mountainArr, left + 1, mountainArr.Length() - 1, false);
}
return(index);
}
/// <summary>
/// Find in Mountain Array (Mine)
/// </summary>
/// <param name="target"></param>
/// <param name="mountainArr"></param>
/// <returns></returns>
public static int FindInMountainArray(int target, MountainArray mountainArr)
{
int a = 0, b = mountainArr.Length() - 1;
int peek;
while (true)
{
int curr = (a + b) / 2;
var(left, currValue, right) = (curr - 1 < 0 ? -1 : mountainArr.Get(curr - 1),
mountainArr.Get(curr),
curr + 1 >= mountainArr.Length() ? mountainArr.Length() : mountainArr.Get(curr + 1));
if (currValue > left && currValue > right)
{
peek = curr;
break;
}
if (currValue < right)
{
a = curr + 1;
}
else
{
b = curr - 1;
}
}
int res = FindInMountainArrayHelper(target, mountainArr, 0, peek);
if (res != -1)
{
return(res);
}
return(FindInMountainArrayHelper(target, mountainArr, peek, mountainArr.Length() - 1, false));
}
private int findMountainTop(MountainArray mountainArr, int left, int right)
{
while (left <= right)
{
int mid = left + (right - left) / 2;
if (mountainArr.Get(mid) < mountainArr.Get(mid + 1))
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
return(left);
}
public int BinarySearch(int target, MountainArray mountainArr, int left, int right, bool flag)
{
if (!flag)
{
target *= -1;
}
while (left <= right)
{
int mid = left + (right - left) / 2;
int mid_num = mountainArr.Get(mid);
if (!flag)
{
mid_num *= -1;
}
if (mid_num == target)
{
return(mid);
}
else if (mid_num < target)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
return(-1);
}
private int BinarySearch(int target, MountainArray mountainArr, int left, int right, bool inc)
{
while (left <= right)
{
int mid = left + (right - left) / 2;
var v = mountainArr.Get(mid);
if (v == target)
{
return(mid);
}
else if (v > target)
{
if (inc)
{
right = mid - 1;
}
else
{
left = mid + 1;
}
}
else
{
if (inc)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
}
return(-1);
}
public int FindPeak(MountainArray mountainArr, int left, int right)
{
while (left < right)
{
var mid = (left + right) / 2;
if (mountainArr.Get(mid) < mountainArr.Get(mid + 1))
{
left = mid + 1;
}
else
{
right = mid;
}
}
return(left);
}
public int SearchRight(int l, int r, int t, MountainArray arr)
{
while (l <= r)
{
int mid = l + (r - l) / 2;
if (arr.Get(mid) == t)
{
return(mid);
}
else if (arr.Get(mid) > t)
{
l = mid + 1;
}
else
{
r = mid - 1;
}
}
return(-1);
}
private int findInSort(MountainArray mountainArr, int left, int right, int target)
{
while (left < right)
{
int mid = left + (right - left) / 2;
int val = mountainArr.Get(mid);
if (val == target)
{
return(mid);
}
if (val < target)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
return(mountainArr.Get(left) == target ? left : -1);
}
/// <summary>
/// 二分查找
/// 1.先确定山顶
/// 2.先从左侧找
/// 3.如无再从右侧找
/// 双百实现！！!
/// </summary>
/// <param name="target"></param>
/// <param name="mountainArr"></param>
/// <returns></returns>
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int len = mountainArr.Length();
int peakIndex = findMountainTop(mountainArr, 0, len - 1);
if (mountainArr.Get(peakIndex) == target)
{
return(peakIndex);
}
int ret = findInSort(mountainArr, 0, peakIndex - 1, target);
if (ret != -1)
{
return(ret);
}
return(findInReverse(mountainArr, peakIndex + 1, len - 1, target));
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
n = mountainArr.Length();
peak = FindPeak(mountainArr);
if (mountainArr.Get(peak) == target)
{
return(peak);
}
int leftResult = SearchLeft(0, peak, target, mountainArr);
if (leftResult != -1)
{
return(leftResult);
}
return(SearchRight(peak + 1, n - 1, target, mountainArr));
}
int BinarySearch(MountainArray A, int target, int l, int r, bool asc)
{
while (l <= r)
{
int m = (l + r) / 2;
int val = A.Get(m);
if (val == target)
{
return(m);
}
if (asc == val < target)
{
l = m + 1;
}
else
{
r = m - 1;
}
}
return(-1);
}
private int BinarySearchMountainArray(MountainArray mountainArr, int target, int start, int end, bool left = true)
{
while (start <= end)
{
// Use this approach instead of (start + end) / 2 to avoid overflow.
int middle = start + (end - start) / 2;
int currentValue = mountainArr.Get(middle);
if (currentValue == target)
{
return(middle);
}
else if (currentValue > target)
{
if (left)
{
end = middle - 1;
}
else
{
start = middle + 1;
}
}
else
{
if (left)
{
start = middle + 1;
}
else
{
end = middle - 1;
}
}
}
return(-1);
}
private static int FindInMountainArrayHelper(int target, MountainArray mountainArr, int a, int b, bool asc = true)
{
while (a <= b)
{
int curr = (a + b) / 2;
int get = mountainArr.Get(curr);
if (get == target)
{
return(curr);
}
if (get < target)
{
if (asc)
{
a = curr + 1;
}
else
{
b = curr - 1;
}
}
else
{
if (asc)
{
b = curr - 1;
}
else
{
a = curr + 1;
}
}
}
return(-1);
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int n = mountainArr.Length();
int l = 0, r = n - 1, peak = 0;
while (l < r)
{
int m = l + (r - l) / 2;
if (mountainArr.Get(m) < mountainArr.Get(m + 1))
{
l = m + 1;
peak = m + 1;
}
else
{
r = m;
}
}
l = 0;
r = peak;
while (l <= r)
{
int m = l + (r - l) / 2;
int element = mountainArr.Get(m);
if (element == target)
{
return(m);
}
else if (element < target)
{
l = m + 1;
}
else
{
r = m - 1;
}
}
l = peak + 1;
r = n - 1;
while (l <= r)
{
int m = l + (r - l) / 2;
int element = mountainArr.Get(m);
if (element == target)
{
return(m);
}
else if (element > target)
{
l = m + 1;
}
else
{
r = m - 1;
}
}
return(-1);
}
public int FindInMountainArray(int target, MountainArray mountainArr)
{
int left = 0, n = mountainArr.Length(), right = n - 1, peak;
while (left < right)
{
int mid = left + (right - left) / 2, m = mountainArr.Get(mid), m1 = mountainArr.Get(mid + 1);
if (m < m1)
{
left = mid + 1;
}
else
{
right = mid;
}
}
if (mountainArr.Get(left) == target)
{
return(left);
}
peak = left;
left = 0;
right = peak;
while (left < right)
{
int mid = left + (right - left) / 2, m = mountainArr.Get(mid);
if (m == target)
{
return(mid);
}
else if (m < target)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
if (mountainArr.Get(left) == target)
{
return(left);
}
left = peak + 1;
right = n - 1;
while (left < right)
{
int mid = left + (right - left) / 2, m = mountainArr.Get(mid);
if (m == target)
{
return(mid);
}
else if (m > target)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
if (mountainArr.Get(right) == target)
{
return(right);
}
return(-1);
}