C 解法, 执行用时: 2ms, 内存消耗: 288KB, 提交时间: 2019-10-06

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
 
void calc(unsigned int n, int *a)
{
    a[0]=n/(1000*1000*1000);
    a[1]=(n/(1000*1000))%1000;
    a[2]=(n/1000)%1000;
    a[3]=n%1000;
    //printf("%u %d %d %d %d\n", n, a[0], a[1], a[2], a[3]);
}
 
void print(int a)
{
    char *x[]={"", "one", "two", "three",
               "four", "five", "six",
               "seven", "eight", "nine",
               "ten", "eleven", "twelve",
              "thirteen", "fourteen", "fifteen",
              "sixteen", "seventeen", "eighteen",
              "nineteen"};
    char *y[]={"", "", "twenty", "thirty",
              "forty", "fifty", "sixty", "seventy",
              "eighty", "ninety"};
    unsigned flag=0;
    if(a>=100)
    {
        printf("%s hundred", x[a/100]);
        flag=1;
    }
    a%=100;
    if(a>=20)
    {
        if(flag)
        {
            printf(" and ");
        }
        printf("%s", y[a/10]);
        a%=10;
        if(a>0)
        {
            printf(" %s", x[a]);
        }
    }
    else if(a>0)
    {
        if(flag)
        {
            printf(" and ");
        }
        printf("%s", x[a]);
    }
}
 
int main()
{
    unsigned int n;
    while(scanf("%u", &n)!=EOF)
    {
        unsigned flag=0;
        int d[4]={0};
        calc(n ,d);
        if(d[0]!=0)
        {
            print(d[0]);
            printf(" billion");
            flag=1;
        }
        if(d[1]!=0)
        {
            if(flag)
            {
                printf(" ");
            }
            print(d[1]);
            printf(" million");
            flag=1;
        }
        if(d[2]!=0)
        {
            if(flag)
            {
                printf(" ");
            }
            print(d[2]);
            printf(" thousand");
            flag=1;
        }
        if(d[3]!=0)
        {
            if(flag)
            {
                printf(" ");
            }
            print(d[3]);
        }
        printf("\n");
    }
    return 0;
}

C 解法, 执行用时: 2ms, 内存消耗: 296KB, 提交时间: 2021-10-01

#include<stdio.h>
#include<string.h>
void calc(long n,int *a){
    a[3] = n/(1000*1000*1000);//billion
    a[2] = (n/(1000*1000))%1000;//million
    a[1] = (n/1000)%1000;//thousand
    a[0] = n%1000;
};

char *x[20] = {
    "", "one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen"
};
char *y[10] = {
    "","","twenty","thirty","forty","fifty","sixty","seventy","eighty","ninety"
};
char *z[5] = {
    "hundred","thousand","million","billion"
};

void output_int(int a){
    
    int f = 0;
    if(a >= 100){
        printf("%s %s",x[a/100],z[0]);
        f = 1;
    }
    a %= 100;
    
    if(a >= 20){
        if(f){
            printf(" and ");
        }
        
        printf("%s",y[a/10]);
        a %= 10;
        if(a > 0){
            printf(" %s",x[a]);
        }
    }else if(a > 0){
        if(f){
            printf(" and ");
        }
        if(a > 0){
            printf("%s",x[a]);
        }
    }
    
    
}

int main(){
    long n;
    int a[4],f;
    while (scanf("%lu",&n)!=EOF) {
        f = 0;
        memset(a,0,sizeof(a));
        calc(n, a);
        if(a[3]){
            output_int(a[3]);
            printf(" %s",z[3]);
            f = 1;
        }
        
        if(a[2]){
            if(f){
                printf(" ");
            }
            output_int(a[2]);
            printf(" %s",z[2]);
            f = 1;
        }
        
        if(a[1]){
            if(f){
                printf(" ");
            }
            output_int(a[1]);
            printf(" %s", z[1]);
            f = 1;
        }
        
        if(a[0]){
            if(f){
                printf(" ");
            }
            output_int(a[0]);
        }
        
        printf("\n");
        
    }
}