Happy number is similar to magic number, but instead of obtaining sum of the digits we obtain sum of square of the digits. EXAMPLE-1 19 =1²+9²=82 82=8²+2²=68 68=6²+8²=100 100=1²+0²+0²=1 EXAMPLE-2 7=7²=49 49=4²+9²=97 97=9²+7²=130 130=1²+3²+0²=10 10=1²+0²=1 EXAMPLE-3 13=1²+3²=10 10=1²+0²=1 A java program on happy number can be made by extracting digits of the number then adding the square of the digits. If the sum result to 1 then it is a happy number and if it not results to 1 then if the sum is greater than 10 then it digits are re-extracted and then again added it's square of digits. JAVA CODE- import java.util.*; public class happy { int n; happy() {     n=0; } void getNum(int nx) {   n=nx;   } int sum_sq_digits(int d) {     int sum=0;     while(d>0)     {         sum=sum+((d%10)*(d%10));         d=d/10;     }     int s;int c=0;     while(sum>9)   ...
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