题解 | #字符统计#

#include <stdio.h>
#include <stdlib.h>
#include "string.h"
int cmp(const void* p1, const void* p2) {
    return (*(char*) p1) - (*(char*)p2);
}

struct ListNode {
    struct ListNode* next;
    char a;
};

typedef struct {
    struct ListNode* node_string;
    int count_string;
} state_string;

state_string res_nums[1000] = {0};

void add_node(state_string* node_string, struct ListNode* node , int nums ) {

    if ( node_string->count_string == 0 ) {

        node_string->count_string = nums;
        node_string->node_string = node;
    } else {

        struct ListNode *head =node_string->node_string;
         
        while (head->next != NULL) {
            head = head->next ;
        }
        head->next = node;
    }
}


int main() {
    char nums[1000];
    scanf("%s", nums);
    int len = strlen(nums);



    qsort(nums,  len, sizeof(char), cmp);

    for (int i = 0; i < len; i++) {
        // 从1开始计数
        int count = 1;
        while (nums[i] == nums[i + 1]) {
            count++;
            i++;
        }
        struct ListNode* pdata = malloc(sizeof(struct ListNode));
        pdata->next = NULL;
        pdata->a    = nums[i];
        add_node( &res_nums[count], pdata, count);

    }

    for (int i = 1000; i >=0; i--) {

        if ( res_nums[i].count_string !=0)
        {
            struct ListNode* pre =res_nums[i].node_string;
            // 这里循环检查下一个是否为空
            while( pre != NULL)
            {
                printf("%c", pre->a);
                pre = pre->next;
            }

        }
    }

}