uva 10400 Game Show Math

来源：互联网发布：win10解压缩软件编辑：程序博客网时间：2024/06/05 20:18

题意：满足表达式，用DFS记忆化搜索，把到当前运算符所得的结果记录下来，起初用回溯一直错

#include <cstdio>#include <cmath>#include <cstring>#include <iostream>using namespace std;int flag,n,b[101],ans,a[101],vis[100][64001];void dfs(int sum,int deep){    if (deep > n && sum == ans)     {        flag=1;         return;    }    if (flag || deep > n || abs(sum) > 32000)        return;    for (int i = 1; i <= 4; i++)    {        b[deep-1] = i;        int s = 32001;        if (i == 1)             s = sum + a[deep];        if (i == 2)             s = sum - a[deep];        if (i == 3)            s = sum * a[deep];        if (i == 4 && (sum % a[deep] == 0))             s = sum / a[deep];        if (abs(s) <=32000 && vis[deep-1][s] == 0)        {            vis[deep-1][s]=1;            dfs(s,deep+1);        }        if (flag)            return;    }}int main(){     int t;    scanf("%d",&t);    while (t--)    {        scanf("%d",&n);        for (int i = 1; i <= n; i++)            scanf("%d",&a[i]);        scanf("%d",&ans);        flag=0;        memset(vis,0,sizeof(vis));        dfs(a[1],2);        if (flag)        {            for (int i =1 ; i < n; i++)            {                printf("%d",a[i]);                if (b[i] == 1)                    printf("+");                if (b[i] == 2)                     printf("-");                if (b[i] == 3)                    printf("*");                if (b[i] == 4)                    printf("/");            }            printf("%d=%d\n",a[n],ans);        }        else            printf("NO EXPRESSION\n");    }    return 0;}