poj 1654 Area

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求面积，注意用 long long，而用double不行，还有就是最后求出的面积（即sum/2）乘以2 将面积看成多个一半的小正方形，

如果是奇数就面积(sum/2)+0.5 偶数就直接输出

#include <iostream>#include <cstdio>#include <string>#include <cmath>using namespace std;string str;int x, y, flag;void Ijs(int i){    if(i == 5) flag = 1;    else if(i == 8) y += 1;    else if(i == 2) y -= 1;    else if(i == 6) x += 1;    else if(i == 4) x -= 1;    else if(i == 9) x += 1, y += 1;    else if(i == 7) x -= 1, y += 1;    else if(i == 3) x += 1, y -= 1;    else if(i == 1) x -= 1, y -= 1;}int main(){//    #ifndef ONLINE_JUDGE//           freopen("in.txt","r",stdin);//    #endif // ONLINE_JUDGE    int t;    scanf("%d", &t);    while(t--)    {        flag = 0;        x = y = 0;        cin >> str;        if(str[0] == '5')        {            cout << 0 << endl;            continue;        }        int len = str.size();        long long sum = 0;        int kx, ky, a;        kx = 0, ky = 0;        for(int i = 0; i < len; i++)        {            a = str[i]-'0';            Ijs(a);            if(flag) break;            sum += kx*y-x*ky;            kx = x, ky = y;        }        if(sum<0) sum = -sum;        if(sum%2) printf("%I64d.5\n", sum/2);        else printf("%I64d\n", sum/2);    }}