TOP101题解 | BM49#表达式求值#

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 * @author Senky
 * @date 2023.08.25
 * @par url https://www.nowcoder.com/creation/manager/content/584337070?type=column&status=-1
 * 返回表达式的值
 * @param s string字符串 待计算的表达式
 * @return int整型
 */
int solve(char* s ) 
{
    // write code here
    int len = strlen(s), num_stk[108], num_idx = -1, sign_idx = -1, op = 0, op_l, op_r;
    char sign_stk[108], ch;
    for(int i=0; i<len; i++)
    {
        if((ch=s[i])>='0' && ch<='9')
        {
            op = ch-48;
            int j = i+1;
            while(j<len && (ch=s[j])>='0' && ch<='9'){ op = 10*op+ch-48;   j++; }
            i = j-1;
            num_stk[ ++num_idx ] = op;   continue;
        }
        if(ch=='+' || ch=='-')
        {
            if( !i )
            {
                num_stk[ ++num_idx ] = 0;
                sign_stk[ ++sign_idx ] = ch;
                continue;
            }
            while(sign_idx!=-1 && sign_stk[sign_idx]!='(')
            {
                op_r = num_stk[ num_idx-- ];
                op_l = num_stk[num_idx];
                switch(sign_stk[ sign_idx-- ])
                {
                    case '+' : { num_stk[num_idx] = op_l+op_r;   break; }
                    case '-' : { num_stk[num_idx] = op_l-op_r;   break; }
                    case '*' : { num_stk[num_idx] = op_l*op_r;   break; }
                }
            }
            sign_stk[ ++sign_idx ] = ch;
            continue;
        }
        if(ch == '*')
        {
            if(sign_stk[sign_idx] == '*'){
                op_r = num_stk[ num_idx-- ];
                op_l = num_stk[num_idx];
                num_stk[num_idx] = op_l*op_r;
                sign_idx--;
            }
            sign_stk[ ++sign_idx ] = '*';
            continue;
        }
        if(ch == '('){ sign_stk[ ++sign_idx ] = '(';   continue; }
        while(sign_stk[sign_idx] != '(')
        {
            op_r = num_stk[ num_idx-- ];
            op_l = num_stk[num_idx];
            switch(sign_stk[ sign_idx-- ])
            {
                case '+' : { num_stk[num_idx] = op_l+op_r;   break; }
                case '-' : { num_stk[num_idx] = op_l-op_r;   break; }
                case '*' : { num_stk[num_idx] = op_l*op_r;   break; }
            }
        }
        sign_idx--;
    }
    while(sign_idx != -1)
    {
        op_r = num_stk[ num_idx-- ];
        op_l = num_stk[num_idx];
        switch(sign_stk[ sign_idx-- ])
        {
            case '+' : { num_stk[num_idx] = op_l+op_r;   break; }
            case '-' : { num_stk[num_idx] = op_l-op_r;   break; }
            case '*' : { num_stk[num_idx] = op_l*op_r;   break; }
        }
    }
    return num_stk[0];
}