剑指Offer-38

来源：互联网发布：陈忠徐紫砂壶淘宝假货编辑：程序博客网时间：2024/05/20 05:57

题目：

统计一个数字在排序数组中出现的次数。

实现

// coding = javapublic class Solution38 {    public static int getNumOfK(int[] nums,int k){        if(nums == null || nums.length<1){            return 0;        }        int first = getFirstK(nums,nums.length,0,nums.length-1,k);        int last =getLastK(nums,nums.length,0,nums.length-1,k);        if(first>-1 && last>-1){            return (last-first)+1;        }        return 0;    }    public static int getFirstK(int[] nums,int length,int start,int end,int k){        if(start>end){            return -1;        }        int middle_index = (start+end)/2;        int middle_data = nums[middle_index];        if(middle_data==k){            if(middle_index>0 && nums[middle_index-1]!=k || middle_index==0){                return middle_index;            }            else{                end = middle_index-1;            }        }        else if(middle_data>k){            end = middle_index-1;        }        else {            start = middle_index +1;        }        return getFirstK(nums,length,start,end,k);    }    public static int getLastK(int[] nums,int length,int start,int end,int k){        if(start>end){            return -1;        }        int middle_index = (start+end)/2;        int middle_data = nums[middle_index];        if(middle_data==k){            if(middle_index<length-1 && nums[middle_index+1]!=k || middle_index==length-1){                return middle_index;            }            else{                start = middle_index+1;            }        }        else if(middle_data>k){            end = middle_index-1;        }        else {            start = middle_index +1;        }        return getLastK(nums,length,start,end,k);    }    public static void main(String[] args){        int[] nums = {1,2,3,3,3,6,8};        int count = getNumOfK(nums,3);        System.out.print(count);    }}

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