二分查找 java递归和非递归实现

递归方法

public static int rank(int []a , int x, int lo, int hi){if(hi<lo)return -1;if(a[lo+(hi-lo)/2]>x)return rank(a,x,lo,lo+(hi-lo)/2-1);else if(a[lo+(hi-lo)/2]<x) return rank(a,x,lo+(hi-lo)/2+1,hi);elsereturn a[lo+(hi-lo)/2];}

非递归方法

public static int rank(int[]a,int key){int hi = a.length-1;int lo = 0;while(lo<=hi) {int mid = lo+(hi-lo)/2;if (key > a[mid]) lo = mid +1;else if (key < a[mid]) hi = mid -1;else return a[mid];}return -1;}