leetcode 224. 基本计算器 C语言

实现一个基本的计算器来计算一个简单的字符串表达式的值。

字符串表达式可以包含左括号 ( ，右括号 )，加号 + ，减号 -，非负整数和空格  。

示例 1:

输入: "1 + 1"
输出: 2
示例 2:

输入: " 2-1 + 2 "
输出: 3
示例 3:

输入: "(1+(4+5+2)-3)+(6+8)"
输出: 23
说明：

你可以假设所给定的表达式都是有效的。
请不要使用内置的库函数 eval。

#define true 1
#define false 0

int isDigit(char ch)
{
    if (ch >= '0' && ch <= '9') {
        return true;
    }
    return false;
}

int calculate(char *s)
{
    int len = strlen(s);
    int *stackDigit = (int*)malloc(sizeof(int) * len);
    char *stackOperator = (char*)malloc(sizeof(char) * len);
    int stackDigitTop = -1;
    int stackOperatorTop = -1;
    int i = 0;
    int tempDigit = 0;
    int num1 = 0;
    int num2 = 0;
    int temp = 0;
    for (i = 0; i < len; i++) {
        while (s[i] == ' ') {
            i++;
        }
        if (i == len) {
            break;
        }
        if (isDigit(s[i]) == true) {
            tempDigit = s[i] - '0';
            i++;
            while (isDigit(s[i]) == true) {
                tempDigit = tempDigit * 10 + (s[i] - '0');
                i++;
            }
            i--;
            stackDigitTop++;
            stackDigit[stackDigitTop] = tempDigit;
            while (stackOperatorTop != -1) {
                if (stackOperator[stackOperatorTop] == '+') {
                    num2 = stackDigit[stackDigitTop];
                    stackDigitTop--;
                    num1 = stackDigit[stackDigitTop];
                    stackDigitTop--;
                    temp = num1 + num2;
                    stackDigitTop++;
                    stackDigit[stackDigitTop] = temp;
                } else if (stackOperator[stackOperatorTop] == '-') {
                    num2 = stackDigit[stackDigitTop];
                    stackDigitTop--;
                    num1 = stackDigit[stackDigitTop];
                    stackDigitTop--;
                    temp = num1 - num2;
                    stackDigitTop++;
                    stackDigit[stackDigitTop] = temp;
                } else {
                    break;
                }
                stackOperatorTop--;
            }
            continue;
        } else if (s[i] == '(') {
            stackOperatorTop++;
            stackOperator[stackOperatorTop] = s[i];
        }  else if (s[i] == ')'){
            while (stackOperator[stackOperatorTop] != '(') {
                num2 = stackDigit[stackDigitTop];
                stackDigitTop--;
                num1 = stackDigit[stackDigitTop];
                stackDigitTop--;
                if (stackOperator[stackOperatorTop] == '+') {
                    temp = num1 + num2;
                    stackDigitTop++;
                    stackDigit[stackDigitTop] = temp;
                } else if (stackOperator[stackOperatorTop] == '-') {
                    temp = num1 - num2;
                    stackDigitTop++;
                    stackDigit[stackDigitTop] = temp;
                }
                stackOperatorTop--;
            }
            stackOperatorTop--;
        } else {
            if (stackOperatorTop != -1) {
                while (stackOperatorTop != -1) {
                    if (stackOperator[stackOperatorTop] == '+') {
                        num2 = stackDigit[stackDigitTop];
                        stackDigitTop--;
                        num1 = stackDigit[stackDigitTop];
                        stackDigitTop--;
                        temp = num1 + num2;
                        stackDigitTop++;
                        stackDigit[stackDigitTop] = temp;
                    } else if (stackOperator[stackOperatorTop] == '-') {
                        num2 = stackDigit[stackDigitTop];
                        stackDigitTop--;
                        num1 = stackDigit[stackDigitTop];
                        stackDigitTop--;
                        temp = num1 - num2;
                        stackDigitTop++;
                        stackDigit[stackDigitTop] = temp;
                    } else {
                        break;
                    }
                    stackOperatorTop--;
                }
            }
            stackOperatorTop++;
            stackOperator[stackOperatorTop] = s[i];
        }
    }
    while (stackOperatorTop != -1) {
        num2 = stackDigit[stackDigitTop];
        stackDigitTop--;
        num1 = stackDigit[stackDigitTop];
        stackDigitTop--;
        if (stackOperator[stackOperatorTop] == '+') {
            temp = num1 + num2;
            stackDigitTop++;
            stackDigit[stackDigitTop] = temp;
        } else if (stackOperator[stackOperatorTop] == '-') {
            temp = num1 - num2;
            stackDigitTop++;
            stackDigit[stackDigitTop] = temp;
        }
        stackOperatorTop--;
    }
    return stackDigit[0];
}

 

来源：CSDN

作者：段刘昌

链接：https://blog.csdn.net/DuanLiuchang/article/details/104156804