Cody

# Problem 659. How long is the longest prime diagonal?

Solution 178355

Submitted on 17 Dec 2012
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### Test Suite

Test Status Code Input and Output
1   Pass
%% n = 4; d = 2; %p = isprime(spiral(n));imagesc(p) assert(isequal(prime_spiral(n),d))

ans = Columns 1 through 6 [0x1 logical] [0x1 logical] [0x1 logical] [0] [2x1 logical] [3x1 logical] Columns 7 through 12 [4x1 logical] [3x1 logical] [2x1 logical] [0] [0x1 logical] [0x1 logical] Column 13 [0x1 logical] c1 = 0 0 0 0 1 0 2 1 1 0 0 0 0 ans = Columns 1 through 6 [0x1 logical] [0x1 logical] [0x1 logical] [1] [2x1 logical] [3x1 logical] Columns 7 through 12 [4x1 logical] [3x1 logical] [2x1 logical] [1] [0x1 logical] [0x1 logical] Column 13 [0x1 logical] c2 = 0 0 0 1 0 2 1 1 0 1 0 0 0 ans = 2

2   Pass
%% n = 7; d = 4; assert(isequal(prime_spiral(n),d))

ans = Columns 1 through 6 [1] [2x1 logical] [3x1 logical] [4x1 logical] [5x1 logical] [6x1 logical] Columns 7 through 11 [7x1 logical] [6x1 logical] [5x1 logical] [4x1 logical] [3x1 logical] Columns 12 through 13 [2x1 logical] [0] c1 = 1 0 1 0 3 0 3 1 2 0 1 0 0 ans = Columns 1 through 6 [1] [2x1 logical] [3x1 logical] [4x1 logical] [5x1 logical] [6x1 logical] Columns 7 through 11 [7x1 logical] [6x1 logical] [5x1 logical] [4x1 logical] [3x1 logical] Columns 12 through 13 [2x1 logical] [1] c2 = 1 0 2 0 2 1 3 0 4 0 1 0 1 ans = 4

3   Pass
%% n = 13; d = 5; assert(isequal(prime_spiral(n),d))

ans = Columns 1 through 5 [7x1 logical] [8x1 logical] [9x1 logical] [10x1 logical] [11x1 logical] Columns 6 through 10 [12x1 logical] [13x1 logical] [12x1 logical] [11x1 logical] [10x1 logical] Columns 11 through 13 [9x1 logical] [8x1 logical] [7x1 logical] c1 = 2 0 1 0 5 0 3 1 2 0 1 0 1 ans = Columns 1 through 5 [7x1 logical] [8x1 logical] [9x1 logical] [10x1 logical] [11x1 logical] Columns 6 through 10 [12x1 logical] [13x1 logical] [12x1 logical] [11x1 logical] [10x1 logical] Columns 11 through 13 [9x1 logical] [8x1 logical] [7x1 logical] c2 = 2 0 3 0 2 1 3 0 5 0 1 0 4 ans = 5

4   Fail
%% n = 52; d = 6; assert(isequal(prime_spiral(n),d))

Error: Assertion failed.

5   Fail
%% n = 81; d = 9; assert(isequal(prime_spiral(n),d))

Error: Assertion failed.