Created
May 19, 2017 19:00
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Finding the number of occurrences of an integer in a sorted array using binary search
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// | |
// main.cpp | |
// interview_questions | |
// | |
// Created by Jonathan Nwosu on 25/03/2017. | |
// Copyright © 2017 Jonathan Nwosu. All rights reserved. | |
// | |
#include <stdio.h> | |
#include <iostream> | |
using namespace std; | |
int binaryOccurance(int array[], int size, int x, bool searchFirst){ | |
int low, high, result, mid; | |
low = 0; | |
high = size - 1; | |
result = -1; | |
while (low <= high){ | |
mid = (low+high)/2; | |
if(array[mid] == x){ | |
result = mid; | |
if(searchFirst) | |
high = mid -1; //Go on searching towards the left (lower indices) | |
else | |
low = mid +1; // Go on searching towards the right (higher indices) | |
} | |
else if(x < array[mid]) high = mid -1; | |
else low = mid+1 ; | |
} | |
return result; | |
} | |
int main() { | |
int array[] = {1,1,3,3,5,5,5,5,5,9,9,11}; | |
int size = sizeof(array)/sizeof(array[0]); | |
int x; | |
cout << "Number to find in array: " << endl; | |
cin >> x; | |
//cout << "Appears: "; | |
//cout << findCount(array, size, x) << "times."<< endl; | |
int firstIndex = binaryOccurance(array, size, x, true); | |
if(firstIndex == -1){ | |
printf( "Count of %d is %d",x,0); | |
} else { | |
int lastIndex = binaryOccurance(array, size, x, false); | |
printf("Count of %d is %d",x,lastIndex - firstIndex + 1); | |
} | |
} | |
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