# Leo's程式筆記

## 三角形

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define max(a,b) (a>b)? a:b
#define min(a,b) (a>b)? b:a
int swap(int *a , int *b)
{
    int temp = *a ;
    *a = *b ;
    *b = temp  ;
}

int main()
{
    float tri[3] = {15,3,16};
    int area = 0 ;
    float s = (tri[0] + tri[1] + tri[2]  )/2.0;
    /* input */


    /* bubble sort  */

    for (int i = 0 ; i< 3 ; i ++)
    {
        for (int j = 0 ; j < 3 - i - 1 ; j ++)
        {
            if (tri[j] > tri[j+1])
            {
                swap(tri+j,tri+j+1);
            }
        }
    }


    /* whther is tri  */
    if (!(tri[0] + tri[1] > tri[2] ))
    {
        printf("Cannot form a triangle.\n");
        return 0 ;
    }
    else
    {
        for (int i = 0 ; i < 3 ;  i++)
        {
            if (i != 2 )
            {
                printf("%.0f > ",tri[i]) ;
            }
            else
            {
                printf("%.0f",tri[i]) ;
            }
        }
        printf("\n") ;

        /* type of  */


        if ((tri[0] * tri[0] + tri[1] * tri[1]) > tri[2] * tri[2]  )
        {
            printf("It is acute triangle.");
        }
        else if ((tri[0] * tri[0] + tri[1] * tri[1]) == tri[2] * tri[2])
        {
            printf("It is Right triangle.");
        }
        else if ((tri[0] * tri[0] + tri[1] * tri[1]) < tri[2] * tri[2])
        {
            printf("It is Obtuse triangle.");
        }
        printf("Area = %.2f \n", sqrt(s*(s-tri[0])*(s-tri[1])*(s-tri[2])));
    }

    printf("Hello world!\n");
    return 0;
}

## 回文

int main()
{
    char int_str[100] = {0} ;
    int length = 0 ;
    int isaPalindrome = 1 ;
    printf("Enter your word: ");
    scanf("%s",int_str);
    printf("\nstring length = ");

    /* 判斷多長 */

    for (int i = 0 ; int_str[i]!='\0' ; i ++)
    {
        length ++ ;
//        printf("%d " , int_str[i]);

    }

    printf("%d\n\n",length);
    /* Whether is a 回文 */
    /* odd */

    for (int i = 0 ; i < length /2 ; i ++)
    {
        if (int_str[i] != int_str[length-1 -i])
        {
            printf("It is not a Palindrome.\n");
            return 0 ;
        }
    }
    printf("It is a Palindrome.\n");

    return 0;
}

## 身分證

int Vertify (char *id)
{
    int sum = 0 ;
    int id2number[] = {10,11,12,13,14,15,16,17,34,18,19,20,21,22,35,23,24,25,26,27,28,29,32,30,31,33};
    int firstword = id2number[id[0] - 'A'] ;

    /* first word  */
    sum +=  (firstword/10)  + firstword%10  ;
    /* last word  */
    sum += (id[9]) ;

    /* 1~9 words process  */
    for (int i = 1 ; i < 9 ; i ++)
    {
        sum += id[i] * (9-i) ;
    }
    printf("SUM = %d\n" , sum) ;
    if (sum%10 == 0 )
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

## 插入排序法

int insert_sort (int *arr , int n )
{
    int j = 0 ;
    int temp ; /* store temporary */
    for (int i = 1 ; i < n ; i ++)
    {
        temp = arr[i] ;
        for( j = i ; j > 0 && temp < arr[j-1]; j --)
        {
            /* move back  the array   */
            arr[j] = arr[j-1] ;
        }
        /* insert value to the space of array  */
        arr[j] = temp ;
    }
}

## 最大公因數

int gcd(int a, int b )
{
    if (b == 0)
        return a ;
    else
        return gcd(b, a%b) ;
}

## 生肖

int main()
{
    int ref_year = 2003 ; /* goat year */
    int in_year = 2002 ;
    int delta_years ;
    char *p[12] ={"goat","monkey","chicken","dog","pig","rat","cow","tiger","rabbit","dragon","snake","horse"};
//    printf("Please input your birth year:%d") ;
//    scanf("%d",&in_year) ;


    /* Calculate the diffence btw ref and inyear */

    delta_years = ((in_year - ref_year))%12 ;

    /* negative+12 shift to right index */
    if (delta_years <0)
        delta_years+=12 ;

    printf("Your birth year is ");


    printf("%s",*(p+delta_years)) ;



    return 0;
}

## 閏年

int IsLeap(int years)
{
    if ((years % 4 == 0 && (years % 100) != 0) || (years %400 == 0 ))
    {
        return 1 ;
    }
    else
    {
        return 0 ;
    }
}