顺序遍历map c++

在C语言中，map通常是用结构体实现的，因此要遍历map，可以使用结构体指针和循环遍历的方式。下面是一个示例代码：

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

struct map_node {
    char* key;
    int value;
    struct map_node* next;
};

struct map {
    struct map_node** buckets;
    int num_buckets;
};

struct map* create_map(int num_buckets) {
    struct map* map = malloc(sizeof(struct map));
    map->buckets = calloc(num_buckets, sizeof(struct map_node*));
    map->num_buckets = num_buckets;
    return map;
}

void add_to_map(struct map* map, char* key, int value) {
    int index = abs(hash(key)) % map->num_buckets;
    struct map_node* node = map->buckets[index];
    while (node != NULL) {
        if (strcmp(node->key, key) == 0) {
            node->value = value;
            return;
        }
        node = node->next;
    }
    node = malloc(sizeof(struct map_node));
    node->key = strdup(key);
    node->value = value;
    node->next = map->buckets[index];
    map->buckets[index] = node;
}

int get_from_map(struct map* map, char* key) {
    int index = abs(hash(key)) % map->num_buckets;
    struct map_node* node = map->buckets[index];
    while (node != NULL) {
        if (strcmp(node->key, key) == 0) {
            return node->value;
        }
        node = node->next;
    }
    return 0;
}

void free_map(struct map* map) {
    for (int i = 0; i < map->num_buckets; i++) {
        struct map_node* node = map->buckets[i];
        while (node != NULL) {
            struct map_node* next = node->next;
            free(node->key);
            free(node);
            node = next;
        }
    }
    free(map->buckets);
    free(map);
}

int main() {
    struct map* map = create_map(10);
    add_to_map(map, "foo", 1);
    add_to_map(map, "bar", 2);
    add_to_map(map, "baz", 3);
    for (int i = 0; i < map->num_buckets; i++) {
        struct map_node* node = map->buckets[i];
        while (node != NULL) {
            printf("%s: %d\n", node->key, node->value);
            node = node->next;
        }
    }
    free_map(map);
    return 0;
}

这个示例代码中，我们使用了一个简单的哈希函数来计算字符串的哈希值，然后用哈希值来确定在哪个桶中存储节点。添加节点时，如果发现已经存在相同的键，则更新节点的值。遍历map时，我们使用两层循环，外层循环遍历所有桶，内层循环遍历桶中的所有节点，并打印它们的键和值。最后，我们释放所有节点并销毁map。