多种方法实现查找

线性查找

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;
const int MAX=100;
int arr[MAX];

bool LinSearch(int n,int target){
    for(int i=0;i<n;i++)
        if(arr[i]==target)
            return true;
    return false;
}

int main(){
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++)           //由n控制输入个数
        scanf("%d",&arr[i]);
    int m;
    scanf("%d",&m);
    while(m--){                    ////由m控制比较个数
        int target;
        scanf("%d",&target);
        if(LinSearch(n, target))
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}

二分查找

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;
const int MAX=100;
int arr[MAX];

bool BinarySearch(int n, int target){
    int left=0;
    int right=n-1;
    while(left<=right){
        int middle=left+(right-left)/2;
        if(arr[middle]<target)
            left=middle+1;
        else if(arr[middle]>target)
            right=middle-1;
        else
            return true;
    }
    return false;
}

int main(){
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++)           //由n控制输入个数
        scanf("%d",&arr[i]);
    sort(arr, arr+n);                //二分查找的前提是数组arr要求有序
    int m;
    scanf("%d",&m);
    while(m--){                    ////由m控制比较个数
        int target;
        scanf("%d",&target);
        if(BinarySearch(n, target))
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}

散列查找

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;
const int MAX=100;
int arr[MAX];
int HashTable[MAX];


int main(){
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%d",&arr[i]);
        HashTable[arr[i]]=true;        //出现这个值，就把对应HashTable的值赋值为true
    }           //由n控制输入个数
    int m;
    scanf("%d",&m);
    while(m--){                    ////由m控制比较个数
        int target;
        scanf("%d",&target);
        if(HashTable[target])        //通过target对应HashTable是否有值存在
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}