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一、顺序查找

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
typedef struct {//查找表的数据结构
	int *data;//动态数组基址
	int TableLen;//表长
}SSTable;

void InitTable(SSTable *L) {//初始化一个动态分配的顺序表:5,3,2,4,7,6,1,9,8,0
	L->data = (int*)malloc(sizeof(int) * 10);
	L->TableLen = 10;
	int arr[10] = { 5,3,2,4,7,6,1,9,8,0 };
	for (int i = 0;i < L->TableLen;i++) {
		L->data[i] = arr[i];
	}
}



//顺序查找
int Search_Seq(SSTable ST,int key)//在ST表中查找key，返回key下标，没找到返回-1
{
	int i = 0;
	for (i = 0;i < ST.TableLen;i++) {
		if (ST.data[i] == key) {
			return i;
		}
	}
	//上面还没return出去说明没找到
	return -1;
}

int main()
{
	SSTable ST;
	InitTable(&ST);
	int key = 0;
	printf("请输入要查的元素，将返回给你元素下标：");
	scanf("%d", &key);
	int x = Search_Seq(ST,key);
	if (x != -1) {
		printf("要查元素的下标为:%d", x);
	}
	else {
		printf("表中无该元素");
	}
	return 0;
}

二、折半查找

#include<stdio.h>
#include<stdlib.h>
typedef struct {//查找表的数据结构
	int *data;//动态数组基址
	int TableLen;//表长
}SSTable;

void InitTable(SSTable *L) {//初始化一个动态分配的顺序表:5,3,2,4,7,6,1,9,8,0
	L->data = (int*)malloc(sizeof(int) * 10);
	L->TableLen = 10;
	int arr[10] = { 1,4,7,8,56,89,90,95,100,121 };
	for (int i = 0;i < L->TableLen;i++) {
		L->data[i] = arr[i];
	}
}

//折半查找
//ps：折半查找的数组必须是有序的
//假设我们这里的测试数组是升序:1,4,7,8,56,89,90,95,100,121
int Binary_Search(SSTable ST,int key) {
	int low = 0;
	int high = ST.TableLen - 1;
	int mid = 0;
	while (low <= high) {
		mid = (low + high) / 2;
		if (ST.data[mid] == key) {
			return mid;
		}
		else if (ST.data[mid] > key) {
			high = mid - 1;
		}
		else {
			low = mid + 1;
		}
	}
	//到这里还没return出去，说明没找到
	return -1;
}


int main()
{
	SSTable ST;
	InitTable(&ST);
	int key = 0;
	printf("请输入要查的元素，将返回给你元素下标：");
	scanf("%d", &key);
	int x = Binary_Search(ST, key);
	if (x != -1) {
		printf("要查元素的下标为:%d", x);
	}
	else {
		printf("表中无该元素");
	}
	return 0;
}