C経典二分検索法

#include <stdio.h>
/* key = 9; 1 2 3 4 5 6 7 8 arr 3， 4， 5， 7， 9 ， 11， 21， 23 low = 1 mid = (low + high)/2 = 4 high = 8; one arr[mid] = 7 < 9; so low = mid + 1 = 5; high = 8; mid = (low + high)/2 = 6 two arr[mid] = 11 > 9 so low = 5 , high = mid - 1 = 5 mid = 5; arr[mid] = 9 == key if(key = 10) low = mid + 1 > high */
int main(int argc, const char * argv[])
{
    int findByHalf(int arr[], int len, int key);

    int arr[] = {3, 4 ,  5, 7, 9 , 11, 21, 23};
    int len = sizeof(arr)/sizeof(int);

    int index = findByHalf(arr, len, 88);

    printf("index = %d
", index);
    return 0;
}

int findByHalf(int arr[], int len, int key){
    int low = 0;
    int high = len - 1;

    int mid ;


    while(low <= high){
        mid = (low + high) / 2;
        //    
        if (key > arr[mid]) {
            low = mid + 1;
        //    
        }else if (key > arr[mid]) {
            high = mid - 1;
        }else{
            return mid;
        }

    }
    return  -1;
}

#include <stdio.h>
/* key = 9; 1 2 3 4 5 6 7 8 arr 3， 4， 5， 7， 9 ， 11， 21， 23 low = 1 mid = (low + high)/2 = 4 high = 8; one arr[mid] = 7 < 9; so low = mid + 1 = 5; high = 8; mid = (low + high)/2 = 6 two arr[mid] = 11 > 9 so low = 5 , high = mid - 1 = 5 mid = 5; arr[mid] = 9 == key if(key = 10) low = mid + 1 > high */
int main(int argc, const char * argv[])
{
    int findByHalf(int arr[], int len, int key);

    int arr[] = {3, 4 ,  5, 7, 9 , 11, 21, 23};
    int len = sizeof(arr)/sizeof(int);

    int index = findByHalf(arr, len, 88);

    printf("index = %d
", index);
    return 0;
}

int insertByHalf(int arr[], int len, int key){
    int low = 0;
    int high = len - 1;

    int mid ;


    while(low <= high){
        mid = (low + high) / 2;
        //    
        if (key > arr[mid]) {
            low = mid + 1;
        //    
        }else if (key > arr[mid]) {
            high = mid - 1;
        }else{
            //  arr[mid] == key
            //  key         
            return mid + 1;
        }

    }
    //  low > high    key > arr[mid];
    //  key   low          
    return  low;
}