hdu Polynomial Problem

有点杂乱无章，考虑各种情况就行了。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
#define INF 0x3fffffff
#define MAXN 100001

int main()
{
    int n,m, x, flag, mul, ans;
    char str[MAXN];
    while(~scanf("%d",&x)){
        scanf("%s",str);
        int len = strlen(str);
        int num = -INF;
        flag = 1;
        ans = 0;
        for(int i = 0; i < len; i++){
            if(str[i] == '-'){
                flag = 0;
                if(i + 1 < len && str[i + 1] == 'X')num = 1;
                continue;
            }
            if(str[i] == '+'){
                flag = 1;
                if(i + 1 < len && str[i + 1] == 'X')num = 1;
                continue;
            }
            if(str[i] == 'X'){
                if(i-1<0)num = 1;
                if(!flag)num = -num;flag = 1;
                if((i + 1 < len && str[i+1] != '^')||i+1>=len)ans += num*x, num = -INF;
                continue;
            }
            if(i - 1 >= 0 && str[i] >= '0' && str[i] <= '9' && str[i-1]== '^'){
                if(i + 1 < len && str[i+1] >= '0' && str[i+1]<= '9'){
                    mul = (str[i] -'0')*10 + str[i+1] - '0';
                    i++;
                }
                else mul = str[i] -'0';
                if(!flag)num = -num;flag = 1;
                int mid = x;
                for(int j = 2; j <= mul; j++){
                    mid *= x;
                }
                ans += num * mid;
                num = -INF;
                continue;
            }
            if(str[i] >= '0' &&str[i] <= '9'){
                if(num == -INF)num = str[i] - '0';
                else num = num*10 + str[i] - '0';
            }

        }
        if(num != -INF){
            if(!flag)num = -num;
            ans += num;
        }
        printf("%d\n",ans);
    }
    return 0;
}