C 语言中的深度优先遍历

我们不会在C编程语言中看到Depth First Traversal（或Depth First Search）的实现。 出于参考目的，我们将遵循我们的示例并将其作为我们的图形模型 -

用C实现 (Implementation in C)

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define MAX 5
struct Vertex {
   char label;
   bool visited;
};
//stack variables
int stack[MAX]; 
int top = -1; 
//graph variables
//array of vertices
struct Vertex* lstVertices[MAX];
//adjacency matrix
int adjMatrix[MAX][MAX];
//vertex count
int vertexCount = 0;
//stack functions
void push(int item) { 
   stack[++top] = item; 
} 
int pop() { 
   return stack[top--]; 
} 
int peek() {
   return stack[top];
}
bool isStackEmpty() {
   return top == -1;
}
//graph functions
//add vertex to the vertex list
void addVertex(char label) {
   struct Vertex* vertex = (struct Vertex*) malloc(sizeof(struct Vertex));
   vertex->label = label;  
   vertex->visited = false;     
   lstVertices[vertexCount++] = vertex;
}
//add edge to edge array
void addEdge(int start,int end) {
   adjMatrix[start][end] = 1;
   adjMatrix[end][start] = 1;
}
//display the vertex
void displayVertex(int vertexIndex) {
   printf("%c ",lstVertices[vertexIndex]->label);
}       
//get the adjacent unvisited vertex
int getAdjUnvisitedVertex(int vertexIndex) {
   int i;
   for(i = 0; i < vertexCount; i++) {
      if(adjMatrix[vertexIndex][i] == 1 && lstVertices[i]->visited == false) {
         return i;
      }
   }
   return -1;
}
void depthFirstSearch() {
   int i;
   //mark first node as visited
   lstVertices[0]->visited = true;
   //display the vertex
   displayVertex(0);   
   //push vertex index in stack
   push(0);
   while(!isStackEmpty()) {
      //get the unvisited vertex of vertex which is at top of the stack
      int unvisitedVertex = getAdjUnvisitedVertex(peek());
      //no adjacent vertex found
      if(unvisitedVertex == -1) {
         pop();
      } else {
         lstVertices[unvisitedVertex]->visited = true;
         displayVertex(unvisitedVertex);
         push(unvisitedVertex);
      }
   }
   //stack is empty, search is complete, reset the visited flag        
   for(i = 0;i < vertexCount;i++) {
      lstVertices[i]->visited = false;
   }        
}
int main() {
   int i, j;
   for(i = 0; i < MAX; i++)    // set adjacency {
      for(j = 0; j < MAX; j++) // matrix to 0
         adjMatrix[i][j] = 0;
   }
   addVertex('S');   // 0
   addVertex('A');   // 1
   addVertex('B');   // 2
   addVertex('C');   // 3
   addVertex('D');   // 4
   addEdge(0, 1);    // S - A
   addEdge(0, 2);    // S - B
   addEdge(0, 3);    // S - C
   addEdge(1, 4);    // A - D
   addEdge(2, 4);    // B - D
   addEdge(3, 4);    // C - D
   printf("Depth First Search: ")
   depthFirstSearch(); 
   return 0;   
}

如果我们编译并运行上面的程序，它将产生以下结果 -

输出 (Output)

Depth First Search: S A D B C