C语言刷题 LeetCode 30天挑战 (七)哈希计数法

//Counting Elements

//Given an integer array arr ,count element x such that x + 1 is also in arr

//lf there're duplicates in arr , count them seperately.

//Example 1:

//Input: arr =[1,2,3]

//0utput:2

//Explanation:1 and 2 are counted cause 2 and 3 are in arr.

//Example 2:

//Input: arr =[1,1,3,3,5,5,7,7]

//0utput:0

//Explanation: No numbers are counted, cause there's no 2,4,6, or 8 in arr.

//Example 3:

//Input: arr = [1,3,2,3,5,8]

//Output:3

//Explanation:0,1 and 2 are counted cause 1,2 and 3 are in arr.

//Example 4:

//Input: arr =[1,1,2,2]

//0utput:2

//Explanation:Two is are counted cause 2 is in arr.

cpp 复制代码
#include <stdio.h>

int countElements(int *arr, int arrSize) {
    // Boolean array to mark presence of elements in the input array.
    int elementExists[1002] = {0}; // Supports values from 0 to 1000

    // Mark the presence of elements in the array
    for (int i = 0; i < arrSize; ++i) {
        elementExists[arr[i]] = 1;
    }

    int returnNum = 0;
    // Check if `arr[i] + 1` exists in the array
    for (int i = 0; i < arrSize; ++i) {
        if (elementExists[arr[i] + 1]) {
            returnNum++;
        }
    }

    return returnNum;
}

int main()
{
    int arr[] = {1,1,2,2};
    printf("%d",countElements(arr,sizeof(arr)/sizeof(arr[0])));
    return 0;
}
相关推荐
1 9 J14 分钟前
Java 上机实践4(类与对象)
java·开发语言·算法
passer__jw7672 小时前
【LeetCode】【算法】3. 无重复字符的最长子串
算法·leetcode
passer__jw7672 小时前
【LeetCode】【算法】21. 合并两个有序链表
算法·leetcode·链表
sweetheart7-72 小时前
LeetCode22. 括号生成(2024冬季每日一题 2)
算法·深度优先·力扣·dfs·左右括号匹配
矛取矛求3 小时前
Linux如何更优质调节系统性能
linux
__AtYou__3 小时前
Golang | Leetcode Golang题解之第557题反转字符串中的单词III
leetcode·golang·题解
lb36363636363 小时前
介绍一下数组(c基础)(详细版)
c语言
李元豪3 小时前
【智鹿空间】c++实现了一个简单的链表数据结构 MyList,其中包含基本的 Get 和 Modify 操作,
数据结构·c++·链表
2401_858286113 小时前
L7.【LeetCode笔记】相交链表
笔记·leetcode·链表
UestcXiye4 小时前
《TCP/IP网络编程》学习笔记 | Chapter 9:套接字的多种可选项
c++·计算机网络·ip·tcp