二分查找又称 折半查找 ,是一种效率较高的查找方法,它支持按关键字大小有序排列的有序结构数据快速查找。
循环实现二分查找算法
public static int binarySearchByForeach(int[] arr, int x) { int low = 0; int high = arr.length-1; while(low <= high) { int middle = (low + high)/2; if(x == arr[middle]) { return middle; }else if(x <arr[middle]) { high = middle - 1; }else { low = middle + 1; } } return -1; }
递归实现实现二分查找算法
public static int binarySearch(int[] dataset ,int data,int beginIndex,int endIndex){
int midIndex = (beginIndex+endIndex)/2;
if(data <dataset[beginIndex]||data>dataset[endIndex]||beginIndex>endIndex){
return -1;
}
if(data <dataset[midIndex]){
return binarySearch(dataset,data,beginIndex,midIndex-1);
}else if(data>dataset[midIndex]){
return binarySearch(dataset,data,midIndex+1,endIndex);
}else {
return midIndex;
}
}
使用实例
public static void main(String[] args) { int[] arr = { 6, 12, 33, 87, 90, 97, 108, 561 }; System.out.println("循环查找:" + (binarySearchByForeach(arr, 87) + 1)); System.out.println("递归查找"+binarySearch(arr,3,87,arr.length-1)); }