###### tags: `C++ Lab`
# Chapter 3 (loops)
1. calculate the following sums:
```
S1 = 1 + 2 + ... + n
S2 = 1/2 + 2/3 + ... + n/n+1
S3 = -1 +2 -3 + ... + (-1)^n*n
#include <iostream>
#include <cmath>
using namespace std;
int main() {
int n;
cout << "Input n: ";
cin >> n;
double s1;
for (int i=1;i<=n;i++) {
s1+=i;
}
cout << "s1 = " << s1 << endl;
double s2;
for (int i=1;i<=n;i++) {
s2 += (double)i/(i+1);
}
cout << "s2 = " << s2 << endl;
double s3;
for (int i=1;i<=n;i++) {
s3 += pow(-1,i)*i;
}
cout << "s3 = " << s3 << endl;
return 0;
}
```
2-3. Print Fibonacci series
```
#include <iostream>
using namespace std;
int main(){
int n;
cout << "Input n: ";
cin >> n;
int x=1,y=1;
if(n==0) cout << x;
else if (n==1) cout << x << " " << y;
else {
cout << x << " " << y << " ";
for(int i=1;i<=(n-1);i++){
cout << x+y<<" ";
int t=y;
y=x+y;
x=t;
}
}
return 0;
}
```
4. Calculate power not using cmath
```#include <iostream>
#include <iomanip>
using namespace std;
int main(){
double x,n,t = 1;
cin>>x>>n;
for (int i=0;i<n;i++) { t*=x; }
cout<<fixed<<setprecision(4)<<t<<endl;
return 0;
}
```
5. Print m*n matrix
```
#include <iostream>
using namespace std;
int main() {
int m, n;
cin>>m>>n;
for(int i=0;i<m;i++, cout<<endl)
for(int j=0; j<n; j++)
cout<<((i*n)+j+1)<<" ";
return 0;
}
```
6. Print triangle with height n
```
#include <iostream>
using namespace std;
int main() {
int n;
cin>>n;
for (int i=1; i<=n; i++) {
for(int j=1;j<=i;j++){
cout<<"*";
}
cout<<endl;
}
return 0;
}
```
7. Print rectangle with n rows * m column
```
#include <iostream>
using namespace std;
int main() {
int n,m;
cin>>n>>m;
for(int i=1;i<=n;i++) {
for(int j=1;j<=m;j++) {
if (i==1||i==n||j==1||j==m)
cout<<"*";
else
cout<<" ";
}
cout<<endl;
}
return 0;
}
```
8. Print pascal triangle with height n+1
```
#include <iostream>
using namespace std;
int main() {
int rows,num=1;
cin>>rows;
for(int i=0;i<=rows;i++) {
for(int j=0;j<=i;j++) {
(j==0||i==0)?num=1:num=num*(i-j+1)/j;
cout<<num<<" ";
}
cout<<endl;
}
return 0;
}
```
9. Calculate sum and avg(input n members's value)
```
#include <iostream>
using namespace std;
int main() {
double n,time,sum;
cout<<"Enter the number of athletes in the team: ";
cin>>n;
for(int i=1;i<=n;i++){
cout<<"Input athete #"<<i<<": ";
cin>>time;
sum+=time;
}
cout<<"Total: "<<sum<<endl;
cout<<"Avg: "<<sum/n<<endl;
return 0;
}
```
10. Calculate avg, highest(subject), lowest(subject)
```
#include <iostream>
using namespace std;
int main() {
int i,t,n,high_t,low_t;
double temp,score,sum,high=0.0,low=10.0;
cout<<"Enter the number of subjects in the semester: ";
cin>>n;
for(i=1;i<=n;i++){
cout<<"Input subject #"<<i<<": ";
cin>>score;
sum+=score;
if (score>=high) {
high=score;
high_t=i;
}
if(score<=low){
low=score;
low_t=i;
}
}
cout<<"Avg: "<<sum/n<<endl;
cout<<"Highest: "<<high<<" ";
cout<<"Subject: "<<high_t<<endl;
cout<<"Lowest: "<<low<<" ";
cout<<"Subject: "<<low_t<<endl;
return 0;
}
```
11. Find k in 2^k^>n
```
#include <iostream>
#include <cmath>
using namespace std;
int main() {
int n,k=0;
cin>>n;
while(pow(2,k)<=n) k++;
cout<<k;
return 0;
}
```
12. Find n in 1/2+1/3+...+1/n<"S"
```
#include <iostream>
using namespace std;
int main() {
int n;
double i=2,sum=0;
cin>>n;
while(sum<n) {
sum+=1/i;
i++;
}
cout<<i-1;
return 0;
}
```
13. Print 1-100, every 10 numbers have newline
```
#include <iostream>
using namespace std;
int main() {
for (int i = 1; i <= 100; i++) {
cout << i<<" ";
if (i % 10 == 0) {
cout<<endl;
}
}
return 0;
}
```
14. Print multiplication table
```
#include <iostream>
using namespace std;
int main() {
for(int i=1;i<=10;i++,cout<<endl)
for(int j=1;j<=10;j++)
cout<<i<<" x "<<j<<" = "<<i*j<<endl;
return 0;
}
```
15. Calculate following sums:
S0: n! = 1*2*...*n
S1: 1 + 1/2 + ... + 1/n
S2: 1+ 1/2! + ... + 1/n!
```
#include <iostream>
using namespace std;
int main() {
double n,s0=1,s1=1,s2=1;
cin >> n;
for(int i=1;i<=n;i++) {
s0=s0*i;
s1=s1+(1/i);
s2=s2+(1/s0);
}
cout<<s0<<endl;
cout<<s1<<endl;
cout<<s2<<endl;
return 0;
}
```
16. find 3-digit numbers, abc=a^3^+b^3^+c^3^ (100*a+10*b+c=a^3^+b^3^+c^3^)
```
#include <iostream>
#include <cmath>
using namespace std;
int main() {
int a=0,b=0,c=0;
for(a=0;a<10;a++)
for(b=0;b<=10;b++)
for(c=0;c<=10;c++)
if(100*a+10*b+c==pow(a,3)+pow(b,3)+pow(c,3)) {
cout<<"a="<<a<<" "<<"b="<<b<<" "<<"c="<<c<<" "<<endl;
}
return 0;
}
```
17. Calculate sum of even numbers and average of odd numbers
(Input prime number(encounter) to stop input)
```
#include <iostream>
using namespace std;
int main() {
int num,e_sum=0,o_sum=0,i,t=0,j=1;
double avg=0;
do {
cin>>num;
for(i=2; i<=num; i++) {
if(num%i==0) {
t++;
break;
}
if(num/i==1) {
t=0;
break;
}
}
if(num%2==0) {
e_sum=e_sum+num;
}
else if(num%2!=0&&t!=0){
o_sum=o_sum+num;
avg=o_sum/j;
j++;
}
} while(t!=0);
cout<<"sum of even numbers: "<<e_sum<<endl;
cout<<"average of odd numbers: "<<avg<<endl;
return 0;
}
```
18. How many digits in the number and sum the digits
```
#include <iostream>
#include <string>
using namespace std;
int main() {
string num;
int sum=0,i;
cin>>num;
for(i=0;i<num.length();++i) {
sum+=num[i]-'0';
}
cout<<"Number of digits: "<<i<<endl;
cout<<"Sum of digits: "<<sum;
return 0;
}
```
19. Print all prime numbers from 2 to N
```
#include<iostream>
using namespace std;
int main() {
int i,t=0,j,num;
cin>>num;
for(i=1; i<=num; i++) {
for(j=2; j<i; j++) {
if(i%j==0) {
t++;
break;
}
}
if(t==0 && i!=1) {
cout<<i<<" ";
}
t = 0;
}
return 0;
}
```
20. Factor a number into prime factors
```
#include <iostream>
using namespace std;
int main() {
int num,i=2;
cin>>num;
cout<<num<<" = ";
while(num!=1) {
if(num==i) {
num=num/i;
cout<<i;
}
if(num%i==0) {
num=num/i;
cout<<i<<" x ";
} else {
i++;
}
}
return 0;
}
```
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