用二分法查找满足条件值的最大下标

二分法: 一般用数组存数据 而且该数组还是有序的

如果用链表存的话  那么访问每一个元素是O(n)的这样效率很低  数组可以实现O(1)的访问

下面看一下实现:

public class Bin {public int binarySearch(int []a,int low,int high,int value){int middle = (low+high)/2;if(a[middle]==value){int tem = findNextValue(a, middle,value);return tem;}if(a[middle]>value){if(middle==0){return -1;}return binarySearch(a, low,middle-1, value);}else{if(middle==(a.length-1)){return -1;}return binarySearch(a, middle+1, high, value);}}public int findNextValue(int []a,int middle,int value){int tem;for(int i=middle;i<a.length;i++){if(a[i]!=value){return --i;}}return a.length-1;}public static void main(String[] args) {int []a={1,3,5,7,12,16,16,16,16,19};Bin bin = new Bin();int e = bin.binarySearch(a, 0, a.length-1, 1);if(e<0){System.out.println("cannot find the value");}else{System.out.println("find the value in:"+e);}}}