MATLAB Answers

Index in position 1 exceeds array bounds (must not exceed 1).

조회 수: 2(최근 30일)
Lamour Haithem Firass
Lamour Haithem Firass 2021년 4월 24일
답변: Bob Thompson 2021년 4월 27일
I have the code below for the bellman function the shortest way, and when i debug, it return "index error" in u = e(2, j), I have tried to change the number several times , still return the same problem, how can I solve it.
function [ v_weight, predecessor ] = bellman_ford( v_num, e_num, source, ...
e, e_weight )
%*****************************************************************************80
%
% Purpose:
%
% BELLMAN_FORD finds shortest paths from a given vertex of a weighted directed graph.
%
% Discussion:
%
% The Bellman-Ford algorithm is used.
%
% Each edge of the graph has a weight, which may be negative. However,
% it should not be the case that there is any negative loop, that is,
% a circuit whose total weight is negative.
%
% Licensing:
%
% This code is distributed under the GNU LGPL license.
%
% Modified:
%
% 12 November 2014
%
% Author:
%
% John Burkardt
%
% Input:
%
% integer V_NUM, the number of vertices.
%
% integer E_NUM, the number of edges.
%
% integer SOURCE, the vertex from which distances will
% be calculated.
%
% integer E(2,E_NUM), the edges, given as pairs of
% vertex indices.
%
% real E_WEIGHT(E_NUM), the weight of each edge.
%
% Output:
%
% real V_WEIGHT(V_NUM), the weight of each node,
% that is, its minimum distance from SOURCE.
%
% integer PREDECESSOR(V_NUM), a list of predecessors,
% which can be used to recover the shortest path from any node back to SOURCE.
%
r8_big = 1.0E+30;
%
% Step 1: initialize the graph.
%
v_weight(1:v_num) = r8_big;
v_weight(source) = 0.0;
predecessor(1:v_num) = -1;
% Step 2: Relax edges repeatedly.
for i = 1 : v_num - 1
for j = 1 : e_num + 1
u = e(2,j);
v = e(1,j);
t = v_weight(u) + e_weight(j);
if ( t < v_weight(v) )
v_weight(v) = t;
predecessor(v) = u;
end
end
end
%
% Step 3: check for negative-weight cycles
%
for j = 1 : e_num
u = e(2,j);
v = e(1,j);
if ( v_weight(u) + e_weight(j) < v_weight(v) )
fprintf ( 1, '\n' );
fprintf ( 1, 'BELLMAN_FORD - Fatal error!\n' );
fprintf ( 1, ' Graph contains a cycle with negative weight.\n' );
error ( 'BELLMAN_FORD - Fatal error!' );
end
end
return
end
  댓글 수: 3
Lamour Haithem Firass
Lamour Haithem Firass 2021년 4월 27일
[ v_weight, predecessor ] = bellman_ford( 6, 8, [1 1 2 3 4 5 5 6 ], [2 6 4 2 3 2 4 5 ], [10 8 2 1 -2 -4 -1 1 ])

댓글을 달려면 로그인하십시오.

답변(1개)

Bob Thompson
Bob Thompson 2021년 4월 27일
You're getting the error because your e input is size 1x8, but u = e(2,j) is trying to call the second row of e, which doesn't exist.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by