1049. Counting Ones (30)计算个位数出现次数.

传送门:https://www.patest.cn/contests/pat-a-practise/1049

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
int a[10]={0};
void deal(int n,int value){
    if(n<=0)
        return;
    int one,ten;
    one = n%10;
    n/=10;
    ten=n;
    for (int i=0; i<=one; ++i) {//个位上出现的数统计下来
        a[i]+=value;
    }
    while (ten) {
        a[ten%10]+= (one+1)*value;
        ten/=10;
    }
    for (int i=0; i<10; ++i) {
        a[i]+=value*n;
    }
    a[0]-=value;//第一位是0的情况排除.
    deal(n-1,value*10);
}
int main(){
    int n;
    scanf("%d",&n);
    deal(n,1);
    printf("%d\n",a[1]);
    return 0;
}


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