1.将数组A中的内容和数组B中的内容进行交换。(数组一样大)
char a[] = "Hello world!"; char b[] = "你 好 世 界!"; char c[13] = ""; int left; int right = sizeof(a) - 2; for (left = 0; left <= right; left++) { c[left] = a[left]; a[left] = b[left]; b[left] = c[left]; } printf("a:%s\nb:%s\n", a, b);
2.计算1/1-1/2+1/3-1/4+1/5 +...+ 1/99 - 1/100 的值。
float sum_1 = 0, sum_2 = 0, sum; int i; for (i = 1; i <= 100; i++) { if (i % 2 == 0) { sum_1 += 1 / i; } else { sum_2 += 1 / i; } } sum = sum_2 - sum_1; printf("1-1/2+1/3-1/4+...+1/99-1/100 = %f", sum);
3.数一下 1 到 100 的所有整数中出现多少次数字9
int i =1, count = 0; for ( ; i <= 100; i++) { if (i % 10 == 9) { count++; } if (i / 10 == 9) { count++; } } printf("出现9的次数为:%d\n", count);