Why in the code given below the number of iterations of the second - for loop ('j') decreases at each iteration of first - for loop ('l')?

for l=1:N-1

disp(['l: ',num2str(l)])

for j=1:N-l

disp(['j: ',num2str(j)])

length = length+1;

end

end

The output iterations are showing like this. Why 'j' is decreasing at each iteration of 'l'?

l: 1

j: 1

j: 2

j: 3

j: 4

j: 5

j: 6

j: 7

j: 8

j: 9

l: 2

j: 1

j: 2

j: 3

j: 4

j: 5

j: 6

j: 7

j: 8

l: 3

j: 1

j: 2

j: 3

j: 4

j: 5

j: 6

j: 7

l: 4

j: 1

j: 2

j: 3

j: 4

j: 5

j: 6

l: 5

j: 1

j: 2

j: 3

j: 4

j: 5

l: 6

j: 1

j: 2

j: 3

j: 4

l: 7

j: 1

j: 2

j: 3

l: 8

j: 1

j: 2

l: 9

j: 1

Answer 1

[VBBV]

For each iteration of I , the j counter is reduced by N- I instead of N-1

N = 5;
length = 0;
for I=1:N-1 
      disp(['l: ',num2str(l)])
      %   ------>> I 
        for j=1:N-I
            disp(['j: ',num2str(j)])
            length = length+1;
        end
end

l: 1

j: 1
j: 2
j: 3
j: 4

l: 2

j: 1
j: 2
j: 3

l: 3

j: 1
j: 2

l: 4

j: 1

[VBBV]

Every time J for loop is iterated, the limit for J loop iteration is changed by I for loop counter increment i.e when N = 3 and I increments from 1 to 2 , the max limit for J for loop is changed by 3-1 , 3-2 etc