【C语言基础】C语言一些简单题目（三）

完成猜数字游戏

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>

void Menu() {
	printf("------------------\n");
	printf("欢迎来到猜数字小游戏\n");
	printf("1.开始游戏\n");
	printf("2.退出\n");
	printf("------------------\n");
}

int main() {
	int i = 1;
	while (i) {
		Menu();
		printf("请选择：");
		scanf("%d", &i);
		switch (i)
		{
		case 1:
			printf("-------游戏开始------\n");
			int input = 0;
			unsigned int num = 0;
			/*用srand和rand制造出一个伪随机数*/
			srand((unsigned)time(NULL));
			num = rand() % 100;
			while (1) {
				printf("请猜出你的数字：");
				scanf("%d", &input);
				if (num > input) {
					printf("猜小了！\n");
				}
				else if (num < input) {
					printf("猜大了\n");
				}
				else {
					system("cls");
					printf("恭喜你猜对了!\n");
					break;
				}
			}
			break;
		case 2:
			i = 0;
			break;
		default:
			printf("选择错误");
			break;
		}
	}
	system("pause");
	return 0;
}

写代码可以在整型有序数组中查找想要的数字，找到了返回下标，找不到返回-1.（折半查找） 

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>

typedef int Type;

int binary_search(Type arr[], int sz, int key) {
	if (arr == NULL) {
		return;
	}
	/*二分查找*/
	int left = 0;
	int right = sz - 1;
	
	while (left <= right) {
		/*求出mid的下标*/
		int mid = left + (right - left) / 2;
		if (arr[mid] > key) {
			right = mid - 1;
		}
		else if (arr[mid] < key) {
			left = mid + 1;
		}
		else {
			return mid;
		}
	}
	/*如果到了这里表示没有找到*/
	return -1;
}

int main() {
	Type arr[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	int key = 0;
	int ret = binary_search(arr, sz, key);
	printf("expect 0, actual :%d", ret);
	system("pause");
	return 0;
}