[Python知识库]编程学习.day1-数组

数组(python与C语言对比学习）

一、数组定义

在 连续 的内存空间中，存储 相同类型 的元素叫做数组。

二、数组的创建

1.python

a_list = [1, 2, 3]
print(a_list)
#[1, 2, 3]

2.C语言

#include <stdio.h>
// 创建数字型数组
int main()
{
    int a[3] = {1, 2, 3};
    int count = 3;
    for (size_t i = 0; i < count; i++)
    {
        printf("%d\n", a[i]);
    }
    return 0;
}
// 1
// 2
// 3

// 创建字符型数组
int main()
{
    char a_list[] = {'a','b','c','\0'};
    printf("%s",a_list);
    return 0;
}
// abc

二、数组元素的插入

1.python

a_list.append(4)
a_list.append(5)
print(a_list)
# [1, 2, 3, 4, 5]
a_list.insert(3, 99)
print(a_list)
# [1, 2, 3, 99, 4, 5]

2.C语言

#include <stdio.h>
// a_list = [1,2,3]
	int count = sizeof(a_list) / sizeof(a_list[0]);
    int index = 2;
    int insert = 50;
    int b_list[count + 1];
    for (size_t i = 0; i <= count; i++)
    {
        if (i < index)
        {
            b_list[i] = a_list[i];
        }
        else if (i == index)
        {
            b_list[i] = insert;
        }
        else
        {
            b_list[i] = a_list[i - 1];
        }
    }
    count++;
    printf("B_count = %d\n", count);
    for (size_t i = 0; i < count; i++)
    {
        printf("b%d=%d\n", i, b_list[i]);
    }

    return 0;


// B_count = 4
// b0=1
// b1=2
// b2=50
// b3=3

三、数组的访问

1.python

# a_list = [1, 2, 3, 99, 4, 5]
temp = a_list[2]
print(temp)
# 3

2.C语言

	// b_list ={1,2,50,3}
    int temp  = b_list[3];
    printf("b3=%d",temp);
    // b3=3

四、数组元素更新

python

a_list[2] = 108
print(a_list)
#[1, 2, 108, 99, 4, 5]

C语言

b_list[2]=108;
// b0=1
// b1=2
// b2=108
// b3=3

五、数组元素删除

python

# a_list=[1, 2, 108, 99, 4, 5]
a_list.remove(108)
print(a_list)
# [1, 2, 99, 4, 5]
a_list.pop(2)
print(a_list)
# [1, 2, 4, 5]
a_list.pop()
print(a_list)
# [1, 2, 4]

C语言

#include <stdio.h>
// 按索引删除
int main()
{
    int a_list[] = {1, 2, 108, 99, 4, 5};
    int del_index=3;
    int count = sizeof(a_list)/sizeof(a_list[1]);
    int b_list[count-1];
    for (size_t i = 0; i < count; i++)
    {
        if (i < del_index-1)
        {
            b_list[i] = a_list[i];
        }
        else
        {
            b_list[i] = a_list[i+1];
        }
    }
    printf("B_count = %d\n", count-1);
    for (size_t i = 0; i < count-1; i++)
    {
        printf("b%d=%d\n", i, b_list[i]);
    }
}
————————————————————————————————————————————————————————————————
#include <stdio.h>
// 删除数组元素
int main()
{
    int a_list[] = {1, 2, 108, 99, 4, 5};
    int del_num = 99;
    int count = sizeof(a_list) / sizeof(a_list[1]);
    int b_list[count - 1];
    int i, j = 0;
    while (i < count)
    {
        if (a_list[i] == del_num)
        {
            i++;
        }
        b_list[j]=a_list[i];
        j++;
        i++;
    }
    printf("B_count = %d\n", count - 1);
    for (size_t i = 0; i < count - 1; i++)
    {
        printf("b%d=%d\n", i, b_list[i]);
    }
}

六、巩固练习

例题来自力扣第一题：两数之和

python

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        d = {}
        for i,e in enumerate(nums):
            if target -e in d:
                return [i,d.get(target-e)]
            d[e] = i 

C语言

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* twoSum(int* nums, int numsSize, int target, int* returnSize)
{
    int map[2*numsSize];
    // 建立哈希表
    for (size_t i = 0; i < numsSize; i++)
    {
        map[2*i] = nums[i];
        map[2*i+1] = i;
    }
	// 查找目标
    int j,m;
    for (size_t i = 0; i < numsSize; i++)
    {
        j = target - nums[i];
        m = 2*i+2;
        while (m < 2*numsSize)
        {
            if (j == map[m] && map[m+1] != i)
            {
                int* ret = malloc(sizeof(int) * 2);
                ret[0] = i, ret[1] = map[m+1];
                *returnSize = 2;
                return ret;
            }
            m = m+2;
        }
    }
    return 0;
}

人生苦短，我用python