http://acm.csu.edu.cn/OnlineJudge/problem.php?id=1537
因为给出的式子是必定合法的,只要用两个栈分别保存符号和数字.算出答案后和从左至右算的答案比对即可.
1 #include <iostream> 2 #include <cstdio> 3 #include <cmath> 4 #include <vector> 5 #include <cstring> 6 #include <algorithm> 7 #include <string> 8 #include <set> 9 #include <functional> 10 #include <numeric> 11 #include <sstream> 12 #include <stack> 13 #include <map> 14 #include <queue> 15 16 #define CL(arr, val) memset(arr, val, sizeof(arr)) 17 18 #define ll long long 19 #define inf 0x7f7f7f7f 20 #define lc l,m,rt<<1 21 #define rc m + 1,r,rt<<1|1 22 #define pi acos(-1.0) 23 24 #define L(x) (x) << 1 25 #define R(x) (x) << 1 | 1 26 #define MID(l, r) (l + r) >> 1 27 #define Min(x, y) (x) < (y) ? (x) : (y) 28 #define Max(x, y) (x) < (y) ? (y) : (x) 29 #define E(x) (1 << (x)) 30 #define iabs(x) (x) < 0 ? -(x) : (x) 31 #define OUT(x) printf("%I64d ", x) 32 #define lowbit(x) (x)&(-x) 33 #define Read() freopen("din.txt", "r", stdin) 34 #define Write() freopen("dout.txt", "w", stdout); 35 36 37 using namespace std; 38 39 int main() 40 { 41 //freopen("a.txt","r",stdin); 42 char s[25]; 43 int num; 44 scanf("%s",s); 45 scanf("%d",&num); 46 stack<int>s1; 47 stack<char>s2; 48 int l=strlen(s); 49 for(int i=0;i<l;i++) 50 { 51 if(s[i]>='0'&&s[i]<='9') s1.push(s[i]-'0'); 52 else if(s[i]=='*') 53 { 54 int x=s1.top();s1.pop(); 55 int y=s[i+1]-'0'; 56 s1.push(x*y); 57 i++; 58 } 59 else s2.push('+'); 60 } 61 while(!s2.empty()) 62 { 63 int x=s1.top();s1.pop(); 64 int y=s1.top();s1.pop(); 65 s1.push(x+y); 66 s2.pop(); 67 } 68 int sum=s[0]-'0'; 69 for(int i=1;i<l;i++) 70 { 71 if(s[i]=='+') sum=sum+(s[i+1]-'0'); 72 else if(s[i]=='*') sum=sum*(s[i+1]-'0'); 73 } 74 //printf("%d %d ",s1.top(),sum); 75 if(s1.top()==sum&&sum==num) printf("U "); 76 else if(s1.top()!=num&&sum!=num) printf("I "); 77 else if(s1.top()==num&&sum!=num) printf("M "); 78 else if(s1.top()!=num&&sum==num) printf("L "); 79 return 0; 80 }