数字在排序数组中出现的次数

题目描述

统计一个数字在排序数组中出现的次数。

 

public class Solution {
    public int GetNumberOfK(int [] array , int k) {
        if(array.length == 0)return 0;
        int num1 = getFirst(array, 0, array.length-1, k);
        int num2 = getLast(array, 0, array.length-1, k);
        if(num1 != -1 && num2 != -1) return num2 - num1 +1;
        return 0;
    }

    public int getFirst(int[] array, int l, int r, int k) {
        if(l>r)return -1;
        int mid = (l+r) >> 1;
        if(array[mid]<k)return getFirst(array, mid+1, r, k);
        else if(array[mid]>k)return getFirst(array, l, mid-1, k);
        else if((mid-1>=0) && (array[mid-1] == k)) return getFirst(array, l, mid-1, k);
        else return mid;
    }
    public int getLast(int[] array, int l, int r, int k) {
        int mid = (l+r) >>1;
        int len = array.length;
        while(l<=r) {
            if(array[mid]<k) l = mid+1;
            else if(array[mid]>k) r = mid-1;
            else if(mid+1<len && array[mid+1] == k) l = mid+1;
            else return mid;
            mid = (l+r)>>1;
        }
        return -1;
    }
}