C語言小練習

1.有1、2、3、4個數字，能組成多少個互不相同且無重複數字的三位數？都是多少？（使用數組）

#include<stdio.h>
int main(void) {
	int a[] = {12, 52, 64, 33, 10, 32, 53, 88, 2, 90};
	int num = 0, i, j = 0;
	scanf("%d", &num);
	for (i = 0; i < 10; i++) {
		if (i == 9) {
			a[i] = 0;
			break;
		}
		if (i >= num) {
			j = i + 1;
			a[i] = a[j];
		}
	}
	
	for (i = 0; i < 10; i++) {
		printf("%d\t", a[i]);
	}
}

2.有一個長度爲10的數組{12,52,64,33,10,32,53,88,2,90}，根據下標將其中某個元素值改爲0，將該元素放在數組的最後，並打印數組的每個元素。

#include<stdio.h>
int main(void) {
	int a[] = {12, 52, 64, 33, 10, 32, 53, 88, 2, 90};
	int num = 0, i, j = 0;
	scanf("%d", &num);
	for (i = 0; i < 10; i++) {
		if (i == 9) {
			a[i] = 0;
			break;
		}
		if (i >= num) {
			j = i + 1;
			a[i] = a[j];
		}
	}
	//遍歷 
	for (i = 0; i < 10; i++) {
		printf("%d\t", a[i]);
	}
}

3.遞歸函數

#include<stdio.h>
void judge();
int main(void) {
	judge();
	printf("111");
}

void judge() {
	int d = 0;
	printf("請重新輸入：\n");
	scanf("%d", &d);
	if (d != 0) {
		judge();
	}
	printf("成功了，因爲打的是：%d\n", d);
}

4.函數返回類型             

#include<stdio.h>
int func1();
int func2();
int func3();

int main(void) {
	int i = 0;
	printf("%d\n", func1());
	printf("%d\n", func2());
	printf("%d", i = i + 1);
}

int func1() {
	int i = 1;
	return i += 1;
}

int func2() {
	int i = 1;
	return i + 1;
}

int func3() {
	int i = 1;
	return i = i + 1;
}

5.作用域

#include<stdio.h>
int func(int a);
int y = 0;

int main(void) {
	int x = 0;
	y = func(x);
	//printf("%d", b);
	//return -1;
	printf("1111~~~\n");
	printf("%d", y);
}

int func(int b) {
	printf("%d", b);
	//printf("%d", x);
	
	return 1;
	printf("hahha\n");
}

6.輸入年月日，判斷這天是該年份的第幾天。

#include<stdio.h>
int main(void) {
	int time = 0;
	int day = 0;
	int month = 0;
	int year = 0;
	printf("請輸入你所要查詢的年月日：\n");
	scanf("%d %d %d", &year, &month, &day);
	switch(month) {
  		case 1: time = day;
				break;
        case 2: time = 31 + day;
				break;
        case 3: time = 31 + 28 + day;
				break;
        case 4: time = 31 + 28 + 31 + day;
				break;
        case 5: time = 31 + 28 + 31 + 30 + day;
				break;
        case 6: time = 31 + 28 + 31 + 30 + 31 + day;
				break;
        case 7: time = 31 + 28 + 31 + 30 + 31 + 30 + day;
				break;
        case 8: time = 31 + 28 + 31 + 30 + 31 + 30 + 31 + day;
				break;
        case 9: time = 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + day;
				break;
        case 10: time = 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + day;
				 break;
        case 11: time = 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + day;
				 break;
        case 12: time = 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + day;
				 break;
  		default: break;
	}
	if(((year % 4 == 0 && year % 100 != 0) || (year % 400) == 0 ) ) {
			time=time+1;
	} 
 	printf("此時是該年的第 %d 天\n", time);
}

7、輸入一個正整數將其轉化爲二進制並輸出。（使用數組存儲二進制的每一位）

#include<stdio.h>
int main(void) {
	int num = 0, i, j, a[100];
	scanf("%d", &num);
	for (i = 0; 1; i++) {
		if (num == 1) {
			a[i] = 1;
			break;
		}
		a[i] = num % 2;
		num /= 2;
	}
	
	for (j = i; j > -1; j--) {
		printf("%d", a[j]);
	}
}

8、水仙花數問題

#include<stdio.h>
int main(void) {
	int i, a, b, c;
	for (i = 100; i < 1000; i++) {
		a = i / 100;
		b = i / 10 % 10;            //i / 10 - a * 10
		c = i % 10;
		if (i == a * a * a + b * b * b + c * c * c) {
			printf("%d\n", i);
		}
	}
}