Binary Search Program in C
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Binary search is a fast search algorithm with run-time complexity of Ο(log n). This search algorithm works on the principle of divide and conquer. For this algorithm to work properly, the data collection should be in a sorted form.
Implementation in C
Live Demo#include <stdio.h> #define MAX 20 // array of items on which linear search will be conducted. int intArray[MAX] = {1,2,3,4,6,7,9,11,12,14,15,16,17,19,33,34,43,45,55,66}; void printline(int count) { int i; for(i = 0;i <count-1;i++) { printf("="); } printf("=\n"); } int find(int data) { int lowerBound = 0; int upperBound = MAX -1; int midPoint = -1; int comparisons = 0; int index = -1; while(lowerBound <= upperBound) { printf("Comparison %d\n" , (comparisons +1) ); printf("lowerBound : %d, intArray[%d] = %d\n",lowerBound,lowerBound, intArray[lowerBound]); printf("upperBound : %d, intArray[%d] = %d\n",upperBound,upperBound, intArray[upperBound]); comparisons++; // compute the mid point // midPoint = (lowerBound + upperBound) / 2; midPoint = lowerBound + (upperBound - lowerBound) / 2; // data found if(intArray[midPoint] == data) { index = midPoint; break; } else { // if data is larger if(intArray[midPoint] < data) { // data is in upper half lowerBound = midPoint + 1; } // data is smaller else { // data is in lower half upperBound = midPoint -1; } } } printf("Total comparisons made: %d" , comparisons); return index; } void display() { int i; printf("["); // navigate through all items for(i = 0;i<MAX;i++) { printf("%d ",intArray[i]); } printf("]\n"); } void main() { printf("Input Array: "); display(); printline(50); //find location of 1 int location = find(55); // if element was found if(location != -1) printf("\nElement found at location: %d" ,(location+1)); else printf("\nElement not found."); }
If we compile and run the above program then it would produce following result −
Output
Input Array: [1 2 3 4 6 7 9 11 12 14 15 16 17 19 33 34 43 45 55 66 ] ================================================== Comparison 1 lowerBound : 0, intArray[0] = 1 upperBound : 19, intArray[19] = 66 Comparison 2 lowerBound : 10, intArray[10] = 15 upperBound : 19, intArray[19] = 66 Comparison 3 lowerBound : 15, intArray[15] = 34 upperBound : 19, intArray[19] = 66 Comparison 4 lowerBound : 18, intArray[18] = 55 upperBound : 19, intArray[19] = 66 Total comparisons made: 4 Element found at location: 19
binary_search_algorithm.htm
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