csu

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.

#include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <algorithm>
#include <string>
#include <set>
#include <functional>
#include <numeric>
#include <sstream>
#include <stack>
#include <map>
#include <queue>

#define CL(arr, val)    memset(arr, val, sizeof(arr))

#define ll long long
#define inf 0x7f7f7f7f
#define lc l,m,rt<<1
#define rc m + 1,r,rt<<1|1
#define pi acos(-1.0)

#define L(x)    (x) << 1
#define R(x)    (x) << 1 | 1
#define MID(l, r)   (l + r) >> 1
#define Min(x, y)   (x) < (y) ? (x) : (y)
#define Max(x, y)   (x) < (y) ? (y) : (x)
#define E(x)        (1 << (x))
#define iabs(x)     (x) < 0 ? -(x) : (x)
#define OUT(x)  printf("%I64d
", x)
#define lowbit(x)   (x)&(-x)
#define Read()  freopen("din.txt", "r", stdin)
#define Write() freopen("dout.txt", "w", stdout);


using namespace std;

int main()
{
    //freopen("a.txt","r",stdin);
    char s[25];
    int num;
    scanf("%s",s);
    scanf("%d",&num);
    stack<int>s1;
    stack<char>s2;
    int l=strlen(s);
    for(int i=0;i<l;i++)
    {
        if(s[i]>='0'&&s[i]<='9') s1.push(s[i]-'0');
        else if(s[i]=='*')
        {
            int x=s1.top();s1.pop();
            int y=s[i+1]-'0';
            s1.push(x*y);
            i++;
        }
        else s2.push('+');
    }
    while(!s2.empty())
    {
        int x=s1.top();s1.pop();
        int y=s1.top();s1.pop();
        s1.push(x+y);
        s2.pop();
    }
    int sum=s[0]-'0';
    for(int i=1;i<l;i++)
    {
        if(s[i]=='+') sum=sum+(s[i+1]-'0');
        else if(s[i]=='*') sum=sum*(s[i+1]-'0');
    }
    //printf("%d %d
",s1.top(),sum);
    if(s1.top()==sum&&sum==num) printf("U
");
    else if(s1.top()!=num&&sum!=num) printf("I
");
    else if(s1.top()==num&&sum!=num) printf("M
");
    else if(s1.top()!=num&&sum==num) printf("L
");
    return 0;
}