题目：

题解：

int calculate(char* s) {int n = strlen(s);int ops[n], top = 0;int sign = 1;ops[top++] = sign;int ret = 0;int i = 0;while (i < n) {if (s[i] == ' ') {i++;} else if (s[i] == '+') {sign = ops[top - 1];i++;} else if (s[i] == '-') {sign = -ops[top - 1];i++;} else if (s[i] == '(') {ops[top++] = sign;i++;} else if (s[i] == ')') {top--;i++;} else {long num = 0;while (i < n && s[i] >= '0' && s[i] <= '9') {num = num * 10 + s[i] - '0';i++;}ret += sign * num;}}return ret;
}