查找算法简介及实现

//查找算法：
//        顺序查找
//        二分查找（插值查找，斐波那契查找）
//        二叉排序树查找
//        哈希表查找

#include <iostream>
using namespace std;


/*顺序查找*/
int sequenceSearch(int* arr, int len, int n)
{
    for (int i = 0; i < len; i++)
        if (arr[i] == n)
            return i;

    return -1;
}

/*二分查找（非递归版本）*/
int binarySearch(int* arr, int len, int n)
{
    int low = 0, high = n - 1, mid;
    while (low <= high)
    {
        mid = (low + high) >> 1;
        if (arr[mid] == n)
            return mid;
        else if (arr[mid] < n)
            low = mid + 1;
        else
            high = mid - 1;
    }

    return -1;
}

/*二分查找（递归版本）*/
int binarySearch0(int* arr, int n, int low, int high)
{
    if (low <= high)
    {
        int mid = (low + high) >> 1;

        if (arr[mid] == n)
            return mid;
        else if (arr[mid] < n)
            binarySearch0(arr, n, mid + 1, high);
        else
            binarySearch0(arr, n, low, mid - 1);
    }

    return -1;
}

/*插值查找*/
int insertSearch(int* arr, int len, int n)
{
    int low = 0, high = len - 1, mid;
    while (low <= high)
    {
        if (arr[low] == arr[high]) //处理数组中具有相同值的情况
            if (arr[low] == n)
                return low;
            else
                return -1;

        mid = (int)(1.0*(n - arr[low]) / (arr[high] - arr[low])*(high - low)); //需要转换为double进行计算
        if (arr[mid] == n)
            return mid;
        else if (arr[mid] < n)
            low = mid + 1;
        else
            high = mid - 1;
    }

    return -1;
}



int main()
{
    cout << "请输入数组序列和带查找元素
（格式：序列长度n 元素1 元素2 ... 元素n 带查找元素num）: " << endl;
    int n, *parr, num;
    cin >> n;
    parr = new int[n];
    for (int i = 0; i < n; i++)
        cin >> parr[i];
    cin >> num;

    cout << "
1 顺序查找； 2 二分查找（非递归）； 3 二分查找（递归）； 4 插值查找；
";
    cout << "请选择查找模式：";
    int selection, index;
    while (cin >> selection)
    {
        switch (selection)
        {
        case 1:
            index = sequenceSearch(parr, n, num);
            break;
        case 2:
            index = binarySearch(parr, n, num);
            break;
        case 3:
            index = binarySearch0(parr, num, 0, n - 1);
            break;
        case 4:
            index = insertSearch(parr, n, num);
            break;
        default:
            break;
        }

        if (index == -1)
            cout << "查找失败！" << endl;
        else
            cout << "查找成功！位置：" << index + 1 << endl;

        cout << "
请选择查找模式：";
    }

    return 0;
}