UVa 443 - Humble Numbers

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题目：求由{2,3,5,7}组成那的数字集合的第n个数字。

分析：利用4根指针，对应每个数字当前对应的因子，每次取最小的数值，指针后移。注意相等的情况。

注意：输出的计数法。

#include <stdio.h>#include <stdlib.h>#include <string.h>int d[ 5850 ];int v[4] = {2,3,5,7};int p[4] = {1,1,1,1};int main(){int count = 2; d[1] = 1;while ( count <= 5842 ) {int min = 2000000001;for ( int i = 0 ; i < 4 ; ++ i ) if ( min > v[i]*d[p[i]] )min = v[i]*d[p[i]];for ( int i = 0 ; i < 4 ; ++ i )if ( min == v[i]*d[p[i]] )p[i] ++;d[count ++] = min;}int n;while ( scanf("%d",&n) && n ) {printf("The %d",n);if ( n%100 == 11 || n%100 == 12 || n%100 == 13 )printf("th");else if ( n%10 == 1 )printf("st");else if ( n%10 == 2 )printf("nd");else if ( n%10 == 3 )printf("rd");else printf("th");printf(" humble number is %d.\n",d[n]);}return 0;}