matrix - PROLOG - 元素的总和

Question

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我有 mxn 矩阵 n,m>1:find sum angular elements ex [1 5 2] [3 6 4] sum =1+2+3+4

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Answer 1

你可以试试这个使用累加器。我们逐行遍历矩阵。

sum_of_corners(M, S) :-
    % the current value of the accumulator is 0
    sum_of_corners(M, 0, S).

% when the travel is finished
sum_of_corners([], T, T).

% We work with the current line
sum_of_corners([L | RL], T1, T) :-
    % We get the first element
    L = [C | R],
    % we compute the sum of the extremities of the line
    sum_of_extremities(R, C, T2),
    T3 is T1+T2,
    % we keep on with the rest of the matrix
    sum_of_corners(RL, T3, T).

% we have found the last element of the line
sum_of_extremities([Last], T1, T) :-
    T is T1 + Last.

% we ignore the current element wich is not the last
sum_of_extremities([_ | R], T1, T) :-
    sum_of_extremities(R, T1, T).