二分法怎么添加进去？

Question

定义一个长度为100的int型数组,数组中前n(
n>=1&&n<=100)个元素已经从小到大有序排列。输入一个整数
,使用二分查找法在该数组中查找和相等的元素。如果在数组中
找到,输出找到的第一个元素的下标;否则,输出“Not Found
#include <stdio.h>
int main()
{
int a[100] = {23, 45, 60, 67, 88}, len = 5;
int value;
int i, type, j;
while (scanf ("%d", &value)){
if (value < 0)break;
for (i = 0; i < len; ++i){
if (value == a[i]){
type = 1;
break;
}
else if (a[i] > value){
type = 2;
break;
}
}
if (i >= len){
a[len++] = value;
}
else {
if (type == 1){
for (j = i; j < len-1; ++j){
a[j] = a[j+1];
}
len--;
}
else if (type == 2){
for (j = len; j > i; --j){
a[j] = a[j-1];
}
len++;
a[i] = value;
}
}
for (i = 0; i < len; ++i){
printf ("%5d", a[i]);
}
printf ("\n");
if (len >= 100){
printf ("More than 100!\n");
break;
}
}

}

Answer 1

这样即可实现二分法找到输入数字所在位置

#include <iostream>
#include <stdio.h>

int dichotomy(int arr[], int len, int value)
{
    auto left = 0;
    auto right = len - 1;

    while (left <= right)
    {
        auto mid = (left + right) / 2;
        if (arr[mid] == value)
            return mid;
        if (arr[mid] < value)
            left = mid + 1;
        else
            right = mid - 1;
    }
    return -1;
}

int main()
{
    std::cout << "Hello World!\n";
    int a[100] = { 23, 45, 60, 67, 88 }, len = 5;
    int value;
    int i, type, j;
    int ret_index = 0;

    while (scanf_s("%d", &value)) {
        if (value < 0)break;
        // 二分法查找输入数字所在位置
        ret_index = dichotomy(a, len, value);
        if (ret_index != -1)
        {
            printf("%d\n", ret_index);
        }
        else
        {
            printf("Not Found !\n");
        }
    }
}