乘法表问题

#include "iostream"#include "algorithm"#include "fstream"using namespace std;/*f[i][j][0] 表示在ch[i]~ch[j]之间以某种方式加括号后，结果为af[i][j][1] 表示在ch[i]~ch[j]之间以某种方式加括号后，结果为bf[i][j][2] 表示在ch[i]~ch[j]之间以某种方式加括号后，结果为ca = a*c || b*c || c*ab = a*a || a*b || b*bc = b*a || c*b || c*c*/int f[50][50][3];char chars[3] = {'a', 'b', 'c'};int mul(int n, char ch[]){    for(int i=0; i<n; i++)        for(int k=0; k<3; k++)            f[i][i][k] = (ch[i] == chars[k] ? 1: 0);    /*    a = a*c || b*c || c*a    b = a*a || a*b || b*b    c = b*a || c*b || c*c    */    for(int r=1; r<n; r++) //规模        for(i=0; i<n-r; i++)  //区间左端点        {            int j = i + r;  //区间右端点            for(int k=i; k<j; k++)  //断点            {                f[i][j][0] += f[i][k][0]*f[k+1][j][2] + f[i][k][1]*f[k+1][j][2] + f[i][k][2]*f[k+1][j][0];                f[i][j][1] += f[i][k][0]*f[k+1][j][0] + f[i][k][0]*f[k+1][j][1] + f[i][k][1]*f[k+1][j][1];                f[i][j][2] += f[i][k][1]*f[k+1][j][0] + f[i][k][2]*f[k+1][j][1] + f[i][k][2]*f[k+1][j][2];            }        }    return f[0][n-1][0];}int main(){    ifstream fin("mul.txt");    cout  << "输入字符串：";    char ch[100];    fin >> ch;  cout << ch;    int n = strlen(ch);    cout << "\n结果为a的加括号方式为：" << mul(n, ch) << endl;    fin.close();    return 0;}