#include <stdio.h>

int binarySearchRecursion(int arry[],int low,int high,int target);

int binarySearch(int array[],int low,int high,int target);

int main(int argc, const char * argv[]) {

    int array[] = {1,3,4,5,6,8,9,11,14,15,18,24,33};

    int index = binarySearch(array, 0, 12, 54);

    int item = binarySearchRecursion(array, 0, 12, 8);

    printf("item = %d\n", item);

    if(index == -1) printf("查找的树不存在\n");

    else printf("index = %d\n", index);

    return 0;

}

int binarySearch(int array[],int low,int high,int target){

    if (array == NULL || low >= high) { return -1; }

    while(low<=high){

        int mid = (low+high)/2;

        if(array[mid] > target)

            // 一定要记得  －1

            high = mid - 1;

        else if(array[mid] < target)

            low = mid+1;

        else // 找到

            return mid;

    }

    // target不存在

    return-1;

}

int binarySearchRecursion(int array[],int low,int high, int target){

    if (array == NULL || low >= high) {

        return -1;

    }

    int mid = low + (high - low)/2;

    if(array[mid] == target)

        return mid;

    else if(target < array[mid]){

        return    binarySearchRecursion(array,low,mid-1,target);}

    else{

        return    binarySearchRecursion(array,mid+1, high,target);}

}

int second_find(int array[], int left, int right, int target){

    if (array == NULL || (left>right)) {

        return  -1;

    }

    int mid = (left+right)/2;

    if (array[mid] == target) {

        return mid;

    }else if(array[mid] >target){

        return second_find(array, left, mid-1, target);

    }else{

        return second_find(array, mid+1, right, target);

    }

    return 0;

}

二分查找