C语言第9天，分支循环练习（二）乘法口诀表等

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

int main() {
	int a = 0, b = 0;
	for (a = 1, b = 1; a <= 100; a++) {
		if (b >= 20)
			break;
		if (b % 3 == 1) {
			b = b + 3;
			continue;
		}
		b = b - 5;
	}
	printf("%d %d\n", a,b);

	printf("\n------------------------------\n");


	//求1到100中数字9的个数
	int i = 0;
	int count = 0;
	for (i = 1; i <= 100; i++) {
		if (i % 10 == 9)
			count++;
		if (i / 10 == 9)
			count++;
	}
	printf("%d\n", count);

	printf("\n------------------------------\n");


	//分数求和 -- 计算1/1 - 1/2 + ........+ 1/99 - 1/100的值
	int j = 0;
	double sum = 0;
	int flag = 1;
	for (j = 1; j <= 100; j++) {
		sum += flag*1.0 / j;
		flag = -flag;
	}
	printf("%lf\n", sum);

	printf("\n------------------------------\n");


	//求最大值
	int arr[] = { 1,-2,-3,4,5,11,7,8,9,10 };
	int max = arr[0];
	int k = 0;
	int sz = sizeof(arr) / sizeof(arr[0]);
	for (k = 0; k < sz; k++) {
		if(arr[k] > max){
			max = arr[k];
		}
	}
	printf("max = %d\n", max);
	return 0;
}

8 22

------------------------------
20

------------------------------
0.688172

------------------------------
max = 11

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

int main() {
	//乘法口诀表
	int i = 0;
	int j = 0;
	for (i = 1; i <= 9; i++) {
		for (j = 1; j <= i; j++) {
			printf("%d*%d=%-2d ", i, j, i * j);//%-2d--输出两位数，且左对齐，不加-则右对齐
		}
		printf("\n");
	}

	return 0;
}

1*1=1
2*1=2  2*2=4
3*1=3  3*2=6  3*3=9
4*1=4  4*2=8  4*3=12 4*4=16
5*1=5  5*2=10 5*3=15 5*4=20 5*5=25
6*1=6  6*2=12 6*3=18 6*4=24 6*5=30 6*6=36
7*1=7  7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49
8*1=8  8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64
9*1=9  9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81