For loops allow iterating over a block of code a specified number of times. The document discusses for loops and how they are similar to while loops but with a different syntax. It provides examples of using basic for loops to print numbers in a range, nested for loops to print patterns, and how for loops can be used to check for divisibility between numbers.

1. C++ For Loops
CMP120
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2. Loops
§ We already know how to do if-then-else
§ We already know how to do while loops.
§ We already know how to do nested while loops.
§ Now we will learn how to do for loops.
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3. ForLoops
§ For loops are a short cut for doing while loops so the
components are all the same.
§ Only the syntax of for loops is different.
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4. Imran Zualkernan
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int j = 1;
while(j < 10){
cout << j;
j=j+1;
}
for(int j=1; j<10; j=j+1){
cout << j;
}
1. Initialize 2. Condition
3. Increment
4.Work
For loops are another way or writing
a while loop.

5. Simple Example
§ Write a program that prints numbers from 1 to n. n
is an input.
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6. Imran Zualkernan
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#include <iostream>
using namespace std;
int main()
{
int n;
cin >> n;
for(int i=1; i<=n; i=i+1){
cout << i;
}
return 0;
}

7. Problem
§ Write a program that takes n as input and prints the
following type of ladder. (n=5)
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8. int main()
{
int n;
cin >> n;
for(int j=1; j<=n; j=j+1){
for(int i=1; i<=j; i=i+1){
cout << i;
}
cout << endl;
}
return 0;
}
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j=1
j=2
j=3
j=4
j=5

9. Problem
§ Write a program that prints the following pattern given
an n.
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10. #include <iostream>
using namespace std;
int main()
{
int n;
cin >> n;
for(int j=1; j<=n; j=j+1){
for(int i=1; i<=j; i=i+1){
cout << i;
}
for(int i=1; i<=j; i=i+1){
cout << "*";
}
cout << endl;
}
return 0;
}
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Prints i’s
Prints *’s
j=1
j=2
j=3
j=4
j=5

11. Problem
§ Write a program to produce the following output
based on an input n.
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12. Imran Zualkernan
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Every time through the loop.
1. Print forward from 1 to j
2. Print backward from j to 1
j=1
j=2
j=3
j=4
j=5

13. #include <iostream>
using namespace std;
int main()
{
int n;
cin >> n;
for(int j=1; j<=n; j=j+1){
for(int i=1; i<=j; i=i+1){
cout << i;
}
for(int i=j; i>=1; i=i-1){
cout << i;
}
cout << endl;
}
return 0;
}
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Printing forward from 1 to j
Printing backwards from j to 1
Prints forward
Prints backwards

14. Problem
§ Write a program to produce the following pattern
given a particular value of n.
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15. Imran Zualkernan
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k=1
k=2
k=3
k=4
k=5
J=1
j=1
j=2
j=3
j=4
j=5
i=1 i=3
i=2
Print n rows
For each row k print j sets of stars
For each set of stars j print from 1 to j

16. Imran Zualkernan
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Print k rows
For each row print k sets of stars
For each set of stars print from 1 to j
for (k = 1 to n)
for (j = 1 to k)
for (i = 1 to j)

17. #include <iostream>
using namespace std;
int main()
{
int n;
cin >> n;
for(int k =1; k<=n; k++){
for(int j=1; j<=k; j=j+1){
for(int i=1; i<=j; i=i+1){
cout << "*";
}
cout << " ";
}
cout << endl;
}
return 0;
}
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Print n rows
Print j sets of
stars
Print j stars
k=1
k=2
k=3
k=4
k=5
J=1
j=1
j=2
j=3
j=4
j=5
i=1 i=3
i=2

18. Problem
§ Write a program to produce all the numbers between
a and b that are divisible by c.
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19. Imran Zualkernan
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#include <iostream>
using namespace std;
int main()
{
int a, b, c;
cin >> a >> b >> c;
for(int i = a; i<=b; i=i+1){
if(i%c==0) cout << i << " is divisible by " << c << endl;
}
return 0;
}

20. Summary
§ For loops are just another way of writing while loops.
§ Nested for loops are used with indexs within indexes
§ Multiple for loops can be nested at any level.
§ Each for loop with all it’s four components can be
considered a block of computation.
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