6-10 二分查找 (20 分)

题目地址https://pintia.cn/problem-sets/15/problems/923

就是二分查找裸题，把程序读清楚就差不多了。

本地写的补全的裁判程序

//-----------------------------------------------
//code by mile
//compiled by clion
//no bug
//Always get ACCEPT
//-----------------------------------------------

#include <map>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

#define MAXSIZE 10
#define NotFound 0
typedef int ElementType;
typedef int Position;
typedef struct LNode *List;
struct LNode {
    ElementType Data[MAXSIZE];
    Position Last;
};

List ReadInput();
Position BinarySearch(List L, ElementType X);

using namespace std;

/*********************Start Here**********************************/

int main()
{
    List L;
    ElementType X;
    Position P;

    L = ReadInput();
    scanf("%d", &X);
    P = BinarySearch(L, X);
    printf("%d
", P);

    return 0;
}

List ReadInput()
{
    List L;
    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) scanf("%d", &L->Data[i]);
    L->Last = n;
    return L;
}

Position BinarySearch(List L, ElementType X)
{
    int l = 1, r = L->Last, ans = 0;

    while(l <= r) {
        int mid = (l+r)>>1;
        if(L->Data[mid] >= X) {
            ans = mid, r = mid-1;
        } else l = mid+1;
    }

    if(L->Data[ans] != X) return NotFound;
    else return ans;
}

提交的函数部分代码

Position BinarySearch(List L, ElementType X)
{
    int l = 1, r = L->Last, ans = 0;

    while(l <= r) {
        int mid = (l+r)>>1;
        if(L->Data[mid] >= X) {
            ans = mid, r = mid-1;
        } else l = mid+1;
    }

    if(L->Data[ans] != X) return NotFound;
    else return ans;
}