hdoj5308

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题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5308

题意：给你n个数，每个数都是n，然后把这n个数加减乘除，每个数都必须用一次，且只能一次，并且运算完的数也都得用一次。也就是做n-1次，问能不能得到24，输出过程 xi ? xj 第i个数与第j个数做?运算。

解题思路：没啥好说，脑补题意，比较奇葩，一个一个推过去，找规律。最后附上标程代码。

#include<iostream>#include<cstring>#include<cmath>#include<algorithm>#include<cstdio>using namespace std;int n;int main(){//freopen("data.in","r",stdin);//freopen("dataa.out","w",stdout);while (scanf("%d",&n)!=EOF){if (n>=15){printf("1 + 2\n"); printf("3 + 4\n"); printf("5 + 6\n"); printf("7 + 8\n"); printf("%d + 9\n",n+1);printf("%d / 10\n",n+2); printf("%d / 11\n",n+3); printf("%d / 12\n",n+4); printf("%d / 13\n",n+5);printf("%d * %d\n",n+6,n+7); printf("%d * %d\n",n+8,n+9); printf("%d * %d\n",n+10,n+11); printf("14 - 15\n");int now=n+13; for (int i=16;i<=n;i++){printf("%d * %d\n",i,now); now++;} printf("%d + %d\n",n+12,now); continue;}if (n>=12){printf("1 + 2\n");for (int i=1;i<=n*2-24;i++) printf("%d / %d\n",i*2+1,i*2+2); int num=n*4-46;int now=n+1+n*2-24;if (n!=12){printf("%d - %d\n",n+1,n+2); now++;for (int i=2;i<=n*2-24;i++){printf("%d - %d\n",now,n+1+i); now++;}}int k1=now;printf("%d - %d\n",num+1,num+2); num+=3; now++;for (int i=num;i<=n;i++){printf("%d * %d\n",i,now); now++;}printf("%d + %d\n",k1,now); continue;}if (n>=10){printf("1 + 2\n");for (int i=1;i<=24-n*2;i++) printf("%d / %d\n",1+2*i,2+2*i);printf("%d + %d\n",n+1,n+2); int now=n+26-n*2;for (int i=2;i<=24-n*2;i++) {printf("%d + %d\n",n+1+i,now); now++;}if (n==10) continue;printf("7 - 8\n"); printf("17 * 9\n"); printf("18 * 10\n"); printf("19 * 11\n"); printf("20 + 16\n"); continue;}if (n==9){printf("1 + 2\n"); printf("3 + 10\n"); printf("4 / 5\n"); printf("6 / 7\n"); printf("8 / 9\n");printf("11 - 12\n"); printf("15 - 13\n"); printf("16 - 14\n"); continue;}if (n==8){printf("1 + 2\n"); printf("3 + 9\n"); printf("4 - 5\n"); printf("6 * 11\n"); printf("7 * 12\n");printf("8 * 13\n"); printf("10 + 14\n"); continue;}if (n==7){printf("1 * 2\n"); printf("3 / 4\n"); printf("5 + 6\n"); printf("8 - 9\n"); printf("11 / 10\n"); printf("12 * 7\n"); continue;}if (n<=3){printf("-1\n"); continue;}if (n==6){printf("1 * 2\n"); printf("7 - 3\n"); printf("8 - 4\n"); printf("9 - 5\n"); printf("10 + 6\n"); continue;}if (n==5){printf("1 / 2\n"); printf("6 / 3\n"); printf("4 - 7\n"); printf("5 * 8\n"); continue;}if (n==4){printf("1 * 2\n"); printf("3 + 5\n"); printf("4 + 6\n"); continue;}}return 0;}

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