1.2 二分法

#include <stdio.h>
#include <string.h>
//二分法
int binarySearch(int a[], int start, int end, int min);

int main(void) {
    int a[100];
    for (int i = 0; i<100; i++) a[i] = i;
    printf("the answer is %d\n",binarySearch(a, 0, 100, 0));
    return 0;
}

int binarySearch(int a[], int start, int end, int min) {
    int mid = (start+end)/2;
    int result;
    if (a[mid] == min || start>end) {
        if (a[mid] == min) return mid;
        else return -1;
    } else if (min<a[mid]) return binarySearch(a, start, mid, min);
    else return binarySearch(a, mid, end, min);
        //return 不能缺少，否则
}