g1001_1100.s1095_find_in_mountain_array.Solution Maven / Gradle / Ivy
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Java-based LeetCode algorithm problem solutions, regularly updated
package g1001_1100.s1095_find_in_mountain_array;
// #Hard #Array #Binary_Search #Interactive #2022_02_22_Time_0_ms_(100.00%)_Space_42.1_MB_(37.47%)
public class Solution {
public int findInMountainArray(int target, MountainArray mountainArr) {
int peakIndex = findPeak(mountainArr);
if (target == mountainArr.get(peakIndex)) {
return peakIndex;
}
int leftResult = findInPeakLeft(target, peakIndex, mountainArr);
if (leftResult != -1) {
return leftResult;
}
return findInPeakRight(target, peakIndex, mountainArr);
}
private int findPeak(MountainArray mountainArray) {
int len = mountainArray.length();
int left = 0;
int right = len - 1;
while (left < right) {
int mid = left + (right - left) / 2;
if (mountainArray.get(mid) < mountainArray.get(mid + 1)) {
left = mid + 1;
} else {
right = mid;
}
}
return left;
}
private int findInPeakLeft(int target, int peakIndex, MountainArray mountainArray) {
int leftIndex = 0;
int rightIndex = peakIndex - 1;
while (leftIndex < rightIndex) {
int midIndex = leftIndex + (rightIndex - leftIndex) / 2;
if (target > mountainArray.get(midIndex)) {
leftIndex = midIndex + 1;
} else {
rightIndex = midIndex;
}
}
return target == mountainArray.get(leftIndex) ? leftIndex : -1;
}
private int findInPeakRight(int target, int peakIndex, MountainArray mountainArray) {
int leftIndex = peakIndex + 1;
int rightIndex = mountainArray.length() - 1;
while (leftIndex < rightIndex) {
int midIndex = leftIndex + (rightIndex - leftIndex) / 2;
if (target < mountainArray.get(midIndex)) {
leftIndex = midIndex + 1;
} else {
rightIndex = midIndex;
}
}
return target == mountainArray.get(leftIndex) ? leftIndex : -1;
}
}