How to find the number of times a number appears in a sorted array

Topic: Statistics The number of times a number appears in a sorted array.

Through binary find, find the first occurrence of the position, and then find the last occurrence of the position, subtract can be.

Time complexity O (logn).

Code:

* * * main.cpp * * Created on:2014.6.12 * author:spike//*eclipse CDT, gcc 4.8.1*/#incl  Ude <stdio.h> #include <stdlib.h> #include <string.h> int getfirstk (int* data, int length,  
    int k, int start, int end) {if (Start > End) return-1;  
    int Middleindex = (start + end)/2;  
      
    int middledata = Data[middleindex];  
            if (Middledata = = k) {if (middleindex>0 && data[middleindex-1]!=k) | | middleindex = = 0)  
        return middleindex;  
    else end = MiddleIndex-1;  
    else if (middledata>k) end = MiddleIndex-1;  
    else start = middleindex+1;  
return GETFIRSTK (data, length, K, start, end); int GETLASTK (int* data, int length, int k, int start, int end) {if (Start > End) return-1  
    ;  
    int middleindex = (start+end)/2;  
    int middledata= Data[middleindex]; if (Middledata = =k) {if (middleindex<length-1 && data[middleindex+1]!=k) | | | middleindex = = length-1) r  
        Eturn Middleindex;  
    else start = middleindex+1;  
    else if (Middledata < k) start = middleindex+1;  
    else end = MiddleIndex-1;  
return GETLASTK (data, length, K, start, end);  
    int GETNUMBEROFK (int* data, int length, int k) {int number = 0;  
    if (data = NULL && length <= 0) return number;  
    INT-A-GETFIRSTK (data, length, K, 0, length-1);  
    int last = GETLASTK (data, length, K, 0, length-1);  
    if (> 1 && last >-1) number = last-first+1;  
return number;  
    int main (void) {int data[] = {1, 2, 3, 3, 3, 3, 4, 5};  
    int k = 3;  
    int result = GETNUMBEROFK (data, 8, k);  
      
    printf ("result =%d\n", result);  
return 0; }

Output:

result = 4

This column more highlights: http://www.bianceng.cnhttp://www.bianceng.cn/Programming/sjjg/

Author: csdn Blog Caroline-wendy