diff --git a/problems/0150.逆波兰表达式求值.md b/problems/0150.逆波兰表达式求值.md index 7d4031d7..0f1e9c23 100644 --- a/problems/0150.逆波兰表达式求值.md +++ b/problems/0150.逆波兰表达式求值.md @@ -502,6 +502,67 @@ impl Solution { } ``` +### C: + +```c +int str_to_int(char *str) { + // string转integer + int num = 0, tens = 1; + for (int i = strlen(str) - 1; i >= 0; i--) { + if (str[i] == '-') { + num *= -1; + break; + } + num += (str[i] - '0') * tens; + tens *= 10; + } + return num; +} + +int evalRPN(char** tokens, int tokensSize) { + + int *stack = (int *)malloc(tokensSize * sizeof(int)); + assert(stack); + int stackTop = 0; + + for (int i = 0; i < tokensSize; i++) { + char symbol = (tokens[i])[0]; + if (symbol < '0' && (tokens[i])[1] == '\0') { + + // pop两个数字 + int num1 = stack[--stackTop]; + int num2 = stack[--stackTop]; + + // 计算结果 + int result; + if (symbol == '+') { + result = num1 + num2; + } else if (symbol == '-') { + result = num2 - num1; + } else if (symbol == '/') { + result = num2 / num1; + } else { + result = num1 * num2; + } + + // push回stack + stack[stackTop++] = result; + + } else { + + // push数字进stack + int num = str_to_int(tokens[i]); + stack[stackTop++] = num; + + } + } + + int result = stack[0]; + free(stack); + return result; +} +``` +