java经典编程题（13-15）

【程序13】题目：一个整数(0-10000)，它加上100后是一个完全平方数，再加上168又是一个完全平方数，请问该数是多少？

public class Demo1 {
public static void main(String[] args) {
for(int k=0;k<=100000;k++){
int x = (int) Math.sqrt(k+100);
if(x*x==k+100){
int y = (int) Math.sqrt(k+268);
if(y*y==k+268)
System.out.println(k);
}
}
}
}

【程序14】题目：输入某年某月某日，判断这一天是这一年的第几天？

public class Demo1 {
public static void main(String[] args) {
int day = 0;
int month = 0;
int year = 0;
int sum = 0;
int leap;
System.out.print("请输入年,月,日\n");
Scanner input = new Scanner(System.in);
year = input.nextInt();
month = input.nextInt();
day = input.nextInt();
// 先计算某月以前月份的总天数
switch (month) {
case 1:
sum = 0;
break;
case 2:
sum = 31;
break;
case 3:
sum = 59;
break;
case 4:
sum = 90;
break;
case 5:
sum = 120;
break;
case 6:
sum = 151;
break;
case 7:
sum = 181;
break;
case 8:
sum = 212;
break;
case 9:
sum = 243;
break;
case 10:
sum = 273;
break;
case 11:
sum = 304;
break;
case 12:
sum = 334;
break;
default:
System.out.println("data error");
break;
}
sum = sum + day; //再加上某天的天数
//判断是不是闰年
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))			leap = 1;
else
leap = 0;
// 如果是闰年且月份大于2,总天数应该加一天
if (leap == 1 && month > 2)
sum++;
System.out.println("It is the the day:" + sum);
}
}

【程序15】题目：输入三个整数x,y,z，请把这三个数由小到大输出。

public class Demo1 {
public static void main(String[] args) {
System.out.print("请输入三个数\n");
Scanner input = new Scanner(System.in);
int x=input.nextInt();
int y=input.nextInt();
int z=input.nextInt();
if(x>y){
int temp = y;
y = x;
x = temp;
}
if(x>z){
int temp = z;
z = x;
x = temp;
}
if(y>z){
int temp = z;
z = y;
y = temp;
}
System.out.println("这三个数由小到大:"+x+", "+y+", "+z);
}
}