小学生四则运算

小学生四则运算

#include<stdio.h>
#include<math.h>
#include<time.h>
int main()
{
	int i = 1;
	int flag = 0;
	float rate = 0;
	char good[4][40] = { "Very good!","Excellent!","Nice work!","Keep up the good work!" };
	char wrong[4][40] = { "No.Please try again.","Wrong.Try once more.","Don’t give up!","Not correct.Keep trying." };
	while(rate<0.75)
	{
		int i = 1;
		while (i<=10)
		{
			srand(time(0));
			int ra3 = rand() % 4 + 0;
			int ra1 = rand() % 10 + 1;
			int ra2 = rand() % 10 + 1;
			int ra4 = rand() % 4 + 0;
			float a;
			char ch[4] = { '+','-','*','/' };
			printf(" %d%c% d=", ra1, ch[ra3], ra2);
			scanf("%f", &a);
			switch (ra3)
			{
			case 0:
				if (a == ra1 + ra2)
				{
					printf(" % s\n", good[ra4]);
					flag++;
					i++;
					break;

				}
				else
				{
					printf("%s\n", wrong[ra4]);
					i++;
					break;
				}

			case 1:
				if (a == ra1 - ra2)
				{
					printf("%s\n", good[ra4]);
					flag++;
					i++;
					break;
				}
				else
				{
					printf("%s\n", wrong[ra4]);
					i++;
					break;
				}
			case 2:
				if (a == ra1 * ra2)
				{
					printf("%s\n", good[ra4]);
					flag++;
					i++;
					break;
				}
				else
				{
					printf("%s\n", wrong[ra4]);
					i++;
					break;
				}
			case 3:
				if (a == (float)ra1 / ra2)
				{
					printf("%s\n", good[ra4]);
					flag++;
					i++;
					break;
				}
				else
				{
					printf("%s\n", wrong[ra4]);
					i++;
					break;
				}
			}
		}
		rate = flag / 10.0;
		printf("%f\n", rate);
		if (rate < 0.75)
			printf("again\n");
	} 

	return 0;
}