设有向图G的十字链表已建立，用C语言函数形式写出求图中各顶点度的算法并打印出来：COUNT_D(G[n],D[n]),G[n]为顶点表，D[n]为存放各顶点度的数组，n为图中顶点的个数。

以下是一个用 C 语言编写的求图中各顶点度的算法，并打印出来的函数形式：

#include <stdio.h>
#include <stdlib.h>

// 边节点
typedef struct EdgeNode {
    int tailVertex;  // 尾顶点
    struct EdgeNode* nextTail;  // 下一个尾节点
    int headVertex;  // 头顶点
    struct EdgeNode* nextHead;  // 下一个头节点
} EdgeNode;

// 顶点节点
typedef struct VertexNode {
    int vertex;  // 顶点
    EdgeNode* firstIn;  // 第一个入边
    EdgeNode* firstOut;  // 第一个出边
} VertexNode;

// 图
typedef struct Graph {
    VertexNode* vertices;  // 顶点表
    int numVertices;  // 顶点个数
} Graph;

// 初始化图
Graph* initGraph(int numVertices) {
    Graph* graph = (Graph*)malloc(sizeof(Graph));
    
    graph->vertices = (VertexNode*)malloc(numVertices * sizeof(VertexNode));
    for (int i = 0; i < numVertices; ++i) {
        graph->vertices[i].vertex = i;
        graph->vertices[i].firstIn = NULL;
        graph->vertices[i].firstOut = NULL;
    }
    
    graph->numVertices = numVertices;
    
    return graph;
}

// 添加边
void addEdge(Graph* graph, int tailVertex, int headVertex) {
    EdgeNode* newEdge = (EdgeNode*)malloc(sizeof(EdgeNode));
    newEdge->tailVertex = tailVertex;
    newEdge->headVertex = headVertex;
    
    newEdge->nextTail = graph->vertices[tailVertex].firstOut;
    graph->vertices[tailVertex].firstOut = newEdge;
    
    newEdge->nextHead = graph->vertices[headVertex].firstIn;
    graph->vertices[headVertex].firstIn = newEdge;
}

// 求图中各顶点度
void countDegrees(Graph* graph, int* degrees) {
    for (int i = 0; i < graph->numVertices; ++i) {
        degrees[i] = 0;
        
        EdgeNode* curEdge = graph->vertices[i].firstOut;
        while (curEdge) {
            degrees[i]++;
            curEdge = curEdge->nextTail;
        }
        
        curEdge = graph->vertices[i].firstIn;
        while (curEdge) {
            degrees[i]++;
            curEdge = curEdge->nextHead;
        }
    }
}

// 打印图中各顶点度
void printDegrees(int* degrees, int numVertices) {
    for (int i = 0; i < numVertices; ++i) {
        printf("顶点 %d 的度为：%d\n", i, degrees[i]);
    }
}

int main() {
    int numVertices = 5;  // 图的顶点数
    Graph* graph = initGraph(numVertices);
    
    // 添加边
    addEdge(graph, 0, 1);
    addEdge(graph, 0, 4);
    addEdge(graph, 1, 2);
    addEdge(graph, 1, 3);
    addEdge(graph, 1, 4);
    addEdge(graph, 2, 3);
    addEdge(graph, 3, 4);

    int* degrees = (int*)malloc(numVertices * sizeof(int));
    countDegrees(graph, degrees);
    printDegrees(degrees, numVertices);
    
    return 0;
}

在这个示例中，我们使用十字链表表示有向图，创建了一个有5个顶点的图，并添加了一些边。然后，我们使用函数 `countDegrees` 来计算图中各顶点的度，并使用函数 `printDegrees` 打印出来。

希望这个算法对你有所帮助！如有任何疑问，请随时提问。