2.1.17-2.1.18

2.1.17

PlusOne   实现加几操作

#include<stdio.h>
int* plusOne(int A[],int length,int number)
{
    int* index = &A[length-1];
    int i;
    int forward;
    for(i=length;i>0;i--)
    {
        if(i==length)
        {
            *index=*index+number;
        }else
        {
            *index=*index+forward;
        }
        forward=*index/10;
        if(forward==0)
        {
            break;
        }
        *index=*index%10;
        index--;

    }
    return A;
}

void main()
{
    int A[5]={4,2,7,1,9};
    int* b = plusOne(A,5,111);
    printf("%d,%d,%d,%d,%d",b[0],b[1],b[2],b[3],b[4]);
}

2.1.18

Climbing Stairs

CS和CS2是不同的前者是递归，后者是基于循环

#include<stdio.h>
int CS(int sumStairs)
{
    if(sumStairs==1)
    {
        return 1;
    }
    if(sumStairs==2)
    {
        return 2;
    }
    return CS(sumStairs-1)+CS(sumStairs-2);
}
int CS2(int sumStairs)
{
    int pre=0;
    int cur=1;
    int tmp;
    int i=1;
    for(;i<=sumStairs;i++)
    {
        tmp=cur;
        cur=cur+pre;
        pre=tmp;
    }
    return cur;
}
void main()
{
    int sum=CS2(10);
    printf("%d",sum);
}