题目：

题解：

int calculate(char* s) {int n = strlen(s);int stk[n], top = 0;char preSign = '+';int num = 0;for (int i = 0; i < n; ++i) {if (isdigit(s[i])) {num = num * 10 + (int)(s[i] - '0');}if (!isdigit(s[i]) && s[i] != ' ' || i == n - 1) {switch (preSign) {case '+':stk[top++] = num;break;case '-':stk[top++] = -num;break;case '*':stk[top - 1] *= num;break;default:stk[top - 1] /= num;}preSign = s[i];num = 0;}}int ret = 0;for (int i = 0; i < top; i++) {ret += stk[i];}return ret;
}