함수 문제풀이

//1610

#include<stdio.h>
 
char *mysubstr(char *str, int start, int count);
 
int main() {
 
    char arr[101];
    int start,count;
    scanf("%s", &arr);
    scanf("%d %d", &start, &count);
    printf("%s\n", mysubstr (arr, start, count));
    
    return 0;
}
 
char *mysubstr(char *str, int start, int count)
{
    int i;
    char a[1000];
    for (i = start; i < count+start; i++) {
        a[i] = str[i];
    }
    a[i] = '\0';
 
    return &a[start];
}

//1620

#include<stdio.h>
#include<stdlib.h>
 
int su;
 
int hap(int su);
 
int main() {
    scanf("%d", &su);
    printf("%d", hap(su));
    return 0;
}
int hap(int su) {
    int sum = 0, num, i;
    while (1) {
        sum = 0;
        while (su != 0) {
            num = su % 10;
            sum += num;
            su = su / 10;
            printf("num : %d\nsum : %d\n", num, sum);
        }
        su = sum;
        num = 0;
        if (sum <= 9)
            break;
    }
    return sum;
}

//2601

#include<stdio.h>
#include<stdlib.h>
 
int pibo(int num);
 
int main() {
    int num;
    scanf_s("%d", &num);
    printf("%d", pibo(num));
    system("pause");
    return 0;
}
 
int pibo(int num) {
    int i,num2;
    int arr[100];
    for (i = 0; i < 100; i++) {
        arr[i] = i; //arr[0]=1 arr[1]=1
    }
    arr[0] = 1;
    for (i = 2; i < num; i++) {
        arr[i] = arr[i-2] + arr[i - 1];
    }
    return arr[num-1];
}