NOIP2013普及组表达式求值

P1981

这道题其实本身很简单。。
以 ‘+’ 分段，然后对于每一个段(只有乘法)做，然后计算时不要忘了时刻 % 10000
我就是加上最后一个数没有 % 10000。。40分

40pts:

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int P = 10000;
string s;

int calc(int l, int r)
{
    if(l > r) return 0;
    stringstream ss(s.substr(l, r - l + 1));
    int base;
    ss >> base;
    char c; int xx;
    while(ss >> c >> xx)
    {
        xx = xx % P;
        if(c == '*') base = base * xx % P;
    }
    // printf("calc(%d, %d) = %d\n", l, r, base);
    return base;
}

signed main(void)
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    // cin >> s;
    getline(cin, s);
    int lastpos = 0, ans = 0;
    for(int i = 0; i < s.length(); i ++)
    {
        if(s[i] == '+') ans += calc(lastpos, i - 1), ans = ans % P, lastpos = i + 1;
    }
    ans = ans + calc(lastpos, s.length() - 1);
    printf("%d", ans);
}

100:

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int P = 10000;
string s;

int calc(int l, int r)
{
    if(l > r) return 0;
    stringstream ss(s.substr(l, r - l + 1));
    int base;
    ss >> base;
    char c; int xx;
    while(ss >> c >> xx)
    {
        xx = xx % P;
        if(c == '*') base = base * xx % P;
    }
    // printf("calc(%d, %d) = %d\n", l, r, base);
    return base;
}

signed main(void)
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    // cin >> s;
    getline(cin, s);
    int lastpos = 0, ans = 0;
    for(int i = 0; i < s.length(); i ++)
    {
        if(s[i] == '+') ans += calc(lastpos, i - 1), ans = ans % P, lastpos = i + 1;
    }
    ans = (ans + calc(lastpos, s.length() - 1)) % P;
    printf("%d", ans % P);
}