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BinarySearch.java
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53 lines (49 loc) · 1.49 KB
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package util;
public class BinarySearch {
/**
* 二分查找算法
*
* @param srcArray 有序数组
* @param key 查找元素
* @return key的数组下标，没找到返回-1
*/
public static void main(String[] args) {
int srcArray[] = {3,5,11,17,21,23,28,30,32,50,64,78,81,95,101};
System.out.println(binSearch(srcArray, 0, srcArray.length - 1, 81));
}
// 二分查找递归实现
public static int binSearch(int srcArray[], int start, int end, int key) {
int mid = (end - start) / 2 + start;
if (srcArray[mid] == key) {
return mid;
}
if (start >= end) {
return -1;
} else if (key > srcArray[mid]) {
return binSearch(srcArray, mid + 1, end, key);
} else if (key < srcArray[mid]) {
return binSearch(srcArray, start, mid - 1, key);
}
return -1;
}
// 二分查找普通循环实现
public static int binSearch(int srcArray[], int key) {
int mid = srcArray.length / 2;
if (key == srcArray[mid]) {
return mid;
}
int start = 0;
int end = srcArray.length - 1;
while (start <= end) {
mid = (end - start) / 2 + start;
if (key < srcArray[mid]) {
end = mid - 1;
} else if (key > srcArray[mid]) {
start = mid + 1;
} else {
return mid;
}
}
return -1;
}
}