java-二分查找算法

男娘i 2024-04-17 17:08 78阅读 0赞

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[] = {3,5,11,17,21,23,28,30,32,50,64,78,81,95,101,102};
                System.out.println(binSearch(srcArray, 81));
                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;   
            } 
        }