[英]How to find Minimum Cost Path in a directed graph
我正在研究有关在有向图中在线查找最小成本路径的代码,我在 geeksforgeeks 中遇到了此代码,这是代码。
// C++ Program to implement
// the above approach
#include <bits/stdc++.h>
using namespace std;
// Stores minimum-cost of path from source
int minSum = INT_MAX;
// Function to Perform BFS on graph g
// starting from vertex v
void getMinPathSum(unordered_map<int,
vector<pair<int,
int> > >& graph,
vector<bool>& visited,
vector<int> necessary,
int source, int dest, int currSum)
{
// If destination is reached
if (source == dest) {
// Set flag to true
bool flag = true;
// Visit all the intermediate nodes
for (int i : necessary) {
// If any intermediate node
// is not visited
if (!visited[i]) {
flag = false;
break;
}
}
// If all intermediate
// nodes are visited
if (flag)
// Update the minSum
minSum = min(minSum, currSum);
return;
}
else {
// Mark the current node
// visited
visited = true;
// Traverse adjacent nodes
for (auto node : graph) {
if (!visited[node.first]) {
// Mark the neighbour visited
visited[node.first] = true;
// Find minimum cost path
// considering the neighbour
// as the source
getMinPathSum(graph, visited,
necessary, node.first,
dest, currSum + node.second);
// Mark the neighbour unvisited
visited[node.first] = false;
}
}
// Mark the source unvisited
visited = false;
}
}
// Driver Code
int main()
{
// Stores the graph
unordered_map<int, vector<pair<int,
int> > >
graph;
graph[0] = { { 1, 2 }, { 2, 3 }, { 3, 2 } };
graph[1] = { { 4, 4 }, { 0, 1 } };
graph[2] = { { 4, 5 }, { 5, 6 } };
graph[3] = { { 5, 7 }, { 0, 1 } };
graph[4] = { { 6, 4 } };
graph[5] = { { 6, 2 } };
graph[6] = { { 7, 11 } };
// Number of nodes
int n = 7;
// Source
int source = 0;
// Destination
int dest = 6;
// Keeps a check on visited
// and unvisited nodes
vector<bool> visited(n, false);
// Stores intemediate nodes
vector<int> necessary{ 2, 4 };
getMinPathSum(graph, visited, necessary,
source, dest, 0);
// If no path is found
if (minSum == INT_MAX)
cout << "-1\n";
else
cout << minSum << '\n';
return 0;
}
但是当代码运行时出现这样的错误(这只是代码错误的一小部分)
main.cpp:68:19: error: no match for ‘operator=’ (operand types are ‘std::vector’ and ‘bool’)
main.cpp:60:45: error: no match for ‘operator+’ (operand types are ‘int’ and ‘std::vector >’)
main.cpp:46:19: error: no match for ‘operator=’ (operand types are ‘std::vector’ and ‘bool’)
有人可以告诉我如何解决这个问题吗?我不擅长调试
该错误是不言自明的。 第一个错误:在第 68 行,您有
visited = false;
您尝试将bool
分配给vector<bool>
的地方。 第三个错误也是。
第二个错误是您尝试添加 integer 和对向量。
minPathSum
实施不正确。 似乎它在某些时候被不正确地重构,甚至没有尝试编译。
应该访问单独visited
的事件visited[source]
。 和for (auto node: graph)
应该是for (auto node: graph[source])
。 共:
void getMinPathSum(unordered_map<int,
vector<pair<int,
int> > >& graph,
vector<bool>& visited,
vector<int> necessary,
int source, int dest, int currSum)
{
// If destination is reached
if (source == dest) {
// Set flag to true
bool flag = true;
// Visit all the intermediate nodes
for (int i : necessary) {
// If any intermediate node
// is not visited
if (!visited[i]) {
flag = false;
break;
}
}
// If all intermediate
// nodes are visited
if (flag)
// Update the minSum
minSum = min(minSum, currSum);
return;
}
else {
// Mark the current node
// visited
visited[source] = true;
// Traverse adjacent nodes
for (auto node : graph[source]) {
if (!visited[node.first]) {
// Mark the neighbour visited
visited[node.first] = true;
// Find minimum cost path
// considering the neighbour
// as the source
getMinPathSum(graph, visited,
necessary, node.first,
dest, currSum + node.second);
// Mark the neighbour unvisited
visited[node.first] = false;
}
}
// Mark the source unvisited
visited[source] = false;
}
}
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