題目:古典問題:有一對兔子,從出生後第3個月起每個月都生一對兔子,小兔子長到第三個月後每個月又生一對兔子,假如兔子都不死,問每個月的兔子總數爲多少?
public class RabbitQues {
public static int numberOfRabbits(int month){int[] total = new int[month];
if( month < 3){
return 1;
}
total[0] = 1;
total[1] = 1;
for(int x =2 ; x< month; x++){
total[x] = total[x-1] + total[x-2];
}
return total[month - 1];
}
}
}
打印出所有的 "水仙花數 ",所謂 "水仙花數 "是指一個三位數,其各位數字立方和等於該數本身。例如:153是一個 "水仙花數 ",因爲153=1的三次方+5的三次方+3的三次方。
public class NarcissusQues {
public static ArrayList<Integer> getNarcissus(){
ArrayList<Integer> narcissuses = new ArrayList<Integer>();
for(int x = 100; x < 1000;x ++){
int hundreds = x/100;
int tens = x/10 - hundreds*10;
int units = x%10;
if(x == (hundreds*hundreds*hundreds + tens*tens*tens + units*units*units)){
narcissuses.add(x);
}
}
return narcissuses;
}
}
題目:有5個人坐在一起,問第五個人多少歲?他說比第4個人大2歲。問第4個人歲數,他說比第3個人大2歲。問第三個人,又說比第2人大兩歲。問第2個人,說比第一個人大兩歲。最後問第一個人,他說是10歲。請問第五個人多大?
public class AgeQues {
public int calculateAge(int sAge, int addAge, int pNum, int totalP){
if(pNum == totalP){
return sAge;
}
return calculateAge(sAge + addAge, addAge, ++pNum, totalP);
}
}
題目:海灘上有一堆桃子,五隻猴子來分。第一隻猴子把這堆桃子憑據分爲五份,多了一個,這隻猴子把多的一個扔入海中, 拿走了一份。第二隻猴子把剩下的桃子又平均分成五份,又多了一個,它同樣把多的一個扔入海中,拿走了一份,第三、第四、第五隻猴子都是這樣做的,問海灘上原來最少有多少個桃子?
public class MonkeyPeachQues {
public int calculateSmallestPeaches(){
int num = 1;
int numPeach = 0;
while(true){
numPeach = num * 5 + 1;
for(int numMonkey =1; numMonkey<=5;numMonkey++){
if(numPeach <= 5){
break;
}
if(numPeach%5!=1){
break;
}
if(numMonkey==5){
return num*5+1;
}
numPeach = (numPeach-1)*4/5;
}
num++;
}
}
public static void main(String args[]){
System.out.println("The the smallest number of peaches : " + new MonkeyPeachQues().calculateSmallestPeaches()); //3121 peaches.
}
}
題目:一個偶數總能表示爲兩個素數之和。
public class PrimeNumQues {
public static boolean isPrime(int num){
if(num<2){
return false;
}
if(num==2){
return true;
}
for(int i=2;i<Math.sqrt(num);i++){
if(num%i==0){
return false;
}
}
return true;
}
public int[] analysisEven(int even) throws Exception{
if(even%2!=0){
throw new Exception("Not an even number.");
}
if(even <= 2){
throw new Exception("Even number should be bigger than 2.");
}
int[] results = new int[]{-1,-1};
int half = even/2;
for(int num = 2; num <= half; num++){
if(isPrime(num)){
if(isPrime(even - num)){
results[0] = num;
results[1] = even - num;
System.out.println("Result: " + results[0] + ", " + results[1]);
return results;
}
}
}
throw new Exception("This even number can not be divided into two prime numbers.");
}
}
題目:一球從100米高度自由落下,每次落地後反跳回原高度的一半;再落下,求它在 第10次落地時,共經過多少米?第10次反彈多高?
public class BallDownQues {
public static double calculateTotalHeight(double beginHeight, int targetTimes){
double downHeight = 0;
double reboundHeight = 0;
double tempHeight = beginHeight;
for(int num=0;num<targetTimes;num++){
downHeight = downHeight + tempHeight;
tempHeight = tempHeight/2;
if(num < (targetTimes-1)){
reboundHeight = reboundHeight + tempHeight;
System.out.println("Times: " + num + " Down: " + downHeight + " Rebound: " + reboundHeight);
}else{
System.out.println("Times: " + num + " Down: " + downHeight);
System.out.println("Times: " + num + " This time's rebound height: " + tempHeight);
}
}
double totalHeight = reboundHeight+downHeight;
System.out.println("Total Height: " + totalHeight);
return totalHeight;
}
public static void main(String args[]){
BallDownQues.calculateTotalHeight(100,10) ;
}
}
題目: 用JAVA檢查字符串爲數字
public static boolean isDigit(String input){
char[] chars = input.toCharArray();
int charLen = chars.length;
if(charLen==0){
return false;
}
for(int num =0;num<charLen;num++){
if(!Character.isDigit(chars[num])){
return false;
}
}
return true;
}