字符串模拟加减乘除

// 加法
#define MAX_N 1000
string a, b;
int A[MAX_N], B[MAX_N], C[MAX_N+1];  // A + B = C
void solve(){
    int lena = a.size(), lenb = b.size();
    int j = 0;
    for (int i = lena - 1; i >=0; i--)
        A[j++]    = a[i] - ‘0‘;
    j = 0;
    for (int i = lenb - 1; i >= 0; i--)
        A[j++] = a[i] - ‘0‘;
    int temp = 0;
    for (int i = 0; i < MAX_N; i++){
        C[i] = A[i] + B[i] + temp;
        temp = C[i] / 10;
        C[i] = C[i] % 10;
    }
    int maxs = (lena, lenb) - 1;
    if (C[maxs + 1] != 0)
        maxs ++;
    for (int i = max; i >= 0; i--)
        cout << C[i];
}