HDU 1015 Safecracker

题目地址：点击打开链接

思路：本来挺简单的，结果犯了一个大错误，把错误代码也贴上来，要求按字典序最大，只要刚开始从大到小排序就行 ，还有就是明白了老师为啥告诉我们要好好学英语，这样就能用英语定义变量了，不只用a,b,c,d,cf,lol,这些破词来定义了，代码把cf敲成c，结果害的我调了2个小时，每个代码都是一部血泪史啊

错误代码1：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int a,n,flag;
int visit[30];
char b[30];
int c[30],cf[6];
int cmp(const void *_x,const void *_y)
{
	int *x = (int*)_x;
	int *y = (int*)_y;
	return *y - *x;
}
void dfs(int cur)
{
    int i;
    if(flag)
        return;
	if(cur == 5 && (cf[0] - cf[1]*cf[1] + cf[2]*cf[2]*cf[2] - cf[3]*cf[3]*cf[3]*cf[3] + cf[4]*cf[4]*cf[4]*cf[4]*cf[4] == a))
	{
		flag = 1;
		for(i=0; i<5; i++)
		{
			printf("%c",cf[i] + 'A' -1);
		}
		printf("\n");
		return;
	}
	for(i=0; i<n; i++)
	{
		if(visit[i] == 0)
		{
			visit[i] = 1;
			cf[cur] = c[i];
			dfs(cur + 1);
			visit[i] = 0;
		}
	}
}
int main()
{
    int i;
	while(scanf("%d %s",&a,b))
	{
		flag = 0;
		if(a == 0 && strcmp(b,"END") == 0)
			break;
		n = strlen(b);
		memset(visit,0,sizeof(visit));
		for(i=0; i<n; i++)
        {
            c[i] = b[i] - 'A' + 1;
        }
        qsort(c,n,sizeof(int),cmp);
		dfs(0);
		if(flag == 0)
			printf("no solution\n");
	}
	return 0;
}

手贱把判断条件也加入if语句，害的cur=5还往下执行

AC代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int a,n,flag;
int visit[30];
char b[30];
int c[30],cf[6];
int cmp(const void *_x,const void *_y)
{
	int *x = (int*)_x;
	int *y = (int*)_y;
	return *y - *x;
}
void dfs(int cur)
{
    int i;
    if(flag)
        return;
	if(cur == 5)
	{
		if(cf[0] - cf[1]*cf[1] + cf[2]*cf[2]*cf[2] - cf[3]*cf[3]*cf[3]*cf[3] + cf[4]*cf[4]*cf[4]*cf[4]*cf[4] == a)//就是这把cf写成c
		{
			flag = 1;
			for(i=0; i<5; i++)
			{
				printf("%c",cf[i] + 'A' - 1);//注意减1
			}
			printf("\n");
		}
		return;
	}
	for(i=0; i<n; i++)
	{
		if(visit[i] == 0)
		{
			visit[i] = 1;
			cf[cur] = c[i];
			dfs(cur + 1);
			visit[i] = 0;
		}
	}
}
int main()
{
    int i;
	while(scanf("%d%s",&a,b))//这里空不空都不影响结果
	{
		if(a == 0 && strcmp(b,"END") == 0)
			break;
		flag = 0;
		n = strlen(b);
		memset(visit,0,sizeof(visit));
		for(i=0; i<n; i++)
        {
            c[i] = b[i] - 'A' + 1;//注意加1
        }
        qsort(c,n,sizeof(int),cmp);
		dfs(0);
		if(flag == 0)
			printf("no solution\n");
	}
	return 0;
}

AC代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

char a[15];

int cmp(const void *_a,const void *_b)
{
	return *(char*)_b - *(char*)_a;//记得前面还要再加一个*
}

int main()
{
	int target,i,j,k,l,m,n,flag;
	int x1,x2,x3,x4,x5;
	while(scanf("%d %s",&target,a))
	{
		flag = 0;
		if(target == 0 && strcmp(a,"END") == 0)
			break;
		n = strlen(a);
		qsort(a,n,sizeof(a[0]),cmp);
		for(i=0; i<n; i++)
		{
			for(j=0; j<n; j++)
			{
				if(j == i)
					continue;
				for(k=0; k<n; k++)
				{
					if(k == i || k == j)
						continue;
					for(l=0; l<n; l++)
					{
						if(l == i || l == j || l == k)
							continue;
						for(m=0; m<n; m++)
						{
							if(m == i || m == j || m == k || m == l)
								continue;
							x1 = a[i] - 64;
							x2 = a[j] - 64;
							x3 = a[k] - 64;
							x4 = a[l] - 64;
							x5 = a[m] - 64;
							if(x1 - x2*x2 + x3*x3*x3 - x4*x4*x4*x4 + x5*x5*x5*x5*x5 == target)
							{
								flag =1;
								printf("%c%c%c%c%c\n",a[i],a[j],a[k],a[l],a[m]);
								goto loop;
							}
						}
					}
				}
			}
		}
loop:if(!flag)
		 printf("no solution\n");
	}
	return 0;
}