【HDOJ6342】Expression in Memories（模拟）

题意：

给定一个由0123456789+* ?组成的表达式，其中？可以被改为任意其它字符，问修改问号后是否有方案使得表达式合法

len<=5e2，sumlen<=1e5

思路：

 #include <stdio.h>
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
 #include <string>
 #include <algorithm>
 #include <iostream>
 #include <ctype.h>
 #include <limits.h>
 #include <set>
 #include <map>
 #include <vector>
 #include <stack>
 #include <queue>
 #include <list>
 #define left (now<<1)
 #define right ((now<<1)+1)
 #define mid ((l+r)>>1)
 #define fst first
 #define snd second
 using namespace std;
 typedef long long lint;

 const int MAXN = 5e2 + ;

 char str[MAXN];
 int n;
 bool ok[MAXN];

 void init(){
     for(int i = ; i < MAXN; ++i){
         str[i] = '\0';
     }
 }

 int main(){
     int t; scanf("%d",&t);
     while(t--){
         init(); scanf("%s",str); int len = strlen(str); bool zero = false;
         memset(ok,false,sizeof(ok));
         for(int i = ; i < len; ++i){
             if(str[i] == '?'){
                 str[i] = ''; ok[i] = true;
             }
         }

         bool can = true; zero = false;
         if(str[] == '+' || str[] == '*' || str[len - ] == '+' ||str[len - ] == '*'){
             can = false;
         }
         for(int i = ; i < len - ; ++i){
             if((str[i] == '+' || str[i] == '*') && (str[i + ] == '*' || str[i + ] == '+')){
                 can = false; break;
             }
         }
         for(int i = ; i < len; ++i){
             if(isdigit(str[i]) && zero){
                 if(ok[i] == false){
                     can = false; break;
                 }else{
                     str[i] = '+';
                 }
             }
             if(str[i] == '' && (i ==  || !isdigit(str[i - ]))){
                 zero = true;
             }else{
                 zero = false;
             }
         }
         if(str[] == '+' || str[] == '*' || str[len - ] == '+' ||str[len - ] == '*'){
             can = false;
         }
         for(int i = ; i < len - ; ++i){
             if((str[i] == '+' || str[i] == '*') && (str[i + ] == '*' || str[i + ] == '+')){
                 can = false; break;
             }
         }
         if(can){
             printf("%s\n",str);
         }else{
             printf("IMPOSSIBLE\n");
         }
     }
     return ;
 }