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ArrayLocalMinSearch.java
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ArrayLocalMinSearch.java
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package com.algorithms.search.local;
/**
* Algorithms 4th exercise 1.4.18 Find Local Minimal Element In Array With Distinct Numbers
* 算法第4版 习题 1.4.18 查找无重复数值数组中的局部最小元素
*/
public class ArrayLocalMinSearch {
/**
* 暴力搜索实现
* @param data 数据集
* @return (-1:无局部最小元素;其他:某一局部最小元素在数据集的下标序号)
*/
public static int bruteForceSearch(int[] data) {
if (data == null || data.length < 3) {
throw new IllegalArgumentException("Invalid data array.");
}
for (int i = 1; i < data.length - 1; i++) {
if (data[i] < data[i - 1] && data[i] < data[i + 1]) {
return i;
}
}
return -1;
}
/**
* 二分搜索实现
* @param data 数据集
* @return (-1:无局部最小元素;其他:某一局部最小元素在数据集的下标序号)
*/
public static int binarySearch(int[] data) {
if (data == null || data.length < 3) {
throw new IllegalArgumentException("Invalid data array.");
}
int start = 0;
int end = data.length;
while (start <= end) {
int mid = (start + end) / 2;
if (data[mid] < data[mid - 1] && data[mid] < data[mid + 1]) {
return mid;
} else if (data[mid - 1] < data[mid]) {
end = mid - 1;
} else {
start = mid + 1;
}
}
return -1;
}
}