洛谷P1981表达式求值__（作业）

想法比较奇特......（写一步看一步）

//后为Debug的过程；

题目点这里

#include<bits/stdc++.h>
using namespace std;
const int maxn=1e6 + 5;
const int node=1e4;

char ch[maxn],lc='+';
long long sum,s=1,now_a,len;
bool is=true,con=true;

int main()
{
    scanf("%s",ch);
    len = strlen(ch);
    for(int i=0;i<len;i++)
    {
        //printf("ch:%c ",ch[i]);
        if('0'<=ch[i] && ch[i]<='9')
        {
            now_a = (now_a*10%node + (ch[i]-'0')%node)%node;
            //printf("now_a:%lld ",now_a);
        }
        if(i == len-1)
        {
            if(lc=='+') sum = (sum+now_a)%node;
            else
            {
                s = (s*now_a)%node;
                sum = (sum+s)%node;
            }
            //printf("<-1> lc:%c s:%lld sum:%lld\n",lc,s,sum);
        }
        if(ch[i]=='+' && lc=='+')
        {
            sum = (sum+now_a)%node;
            //printf("<1> lc:%c s:%lld sum:%lld\n",lc,s,sum);
            now_a = 0;
        }
        if(ch[i]=='*')
        {
            s = (s*now_a)%node;
            //printf("<2> lc:%c s:%lld sum:%lld\n",lc,s,sum);
            now_a = 0;
            lc = '*';
        }
        if(ch[i]=='+' && lc=='*')
        {
            s = (s*now_a)%node;
            sum = (sum+s)%node;
            //printf("<3> lc:%c s:%lld sum:%lld\n",lc,s,sum);
            now_a = 0;
            s = 1;
            lc = '+';
        }
        //printf("\n\n");
    }
    printf("%lld\n",sum);
    return 0;
}