memset(str,0,16)括号里的都是什么意思
时间: 2024-02-09 20:11:05 浏览: 24
这里的memset函数用于将指定的内存区域按照指定的大小进行赋值操作,将每个字节赋值为特定的值。它的函数原型如下:
```
void *memset(void *s, int c, size_t n);
```
其中,s表示指向要填充的内存块的指针,c表示要填充的值,n表示要填充的字节数。
在这里,memset(str, 0, 16)的含义是将字符数组str的前16个字节全部赋值为0。其中,str表示要赋值的内存块的指针,0表示要赋的值,16表示要赋值的字节数。这行代码的作用是将str数组清空,以便后续再次使用。
相关问题
用C++写一个数字 n 代表生成括号的对数,用于能够生成所有可能的并且 有效的 括号组合的程序
```
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void generateParenthesis(int n, char** result, int* returnSize) {
if (n <= 0) {
return;
}
char* str = (char*)malloc(sizeof(char) * (2 * n + 1));
memset(str, 0, sizeof(char) * (2 * n + 1));
int left = n, right = n;
int pos = 0;
generate(str, left, right, pos, result, returnSize);
free(str);
}
void generate(char* str, int left, int right, int pos, char** result, int* returnSize) {
if (left == 0 && right == 0) {
result[*returnSize] = (char*)malloc(sizeof(char) * (strlen(str) + 1));
strcpy(result[*returnSize], str);
(*returnSize)++;
return;
}
if (left > 0) {
str[pos] = '(';
generate(str, left - 1, right, pos + 1, result, returnSize);
}
if (right > left) {
str[pos] = ')';
generate(str, left, right - 1, pos + 1, result, returnSize);
}
}
int main() {
int n = 3;
int returnSize = 0;
char** result = (char**)malloc(sizeof(char*) * 1000);
generateParenthesis(n, result, &returnSize);
printf("All valid combinations of %d pairs of parentheses:\n", n);
for (int i = 0; i < returnSize; i++) {
printf("%s\n", result[i]);
free(result[i]);
}
free(result);
return 0;
}
```
数据结构:计算器软件 要求: (1)实现大数相加,相减功能 (2)能进行2,8,10,16进制数制转换 (3)能进行判断括号是否匹配、以及对表达式进行求值。用c语言实现代码
以下是一个简单的用C语言实现计算器软件的代码,包括了大数相加相减、进制转换、括号匹配和表达式求值等功能:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX_SIZE 1000
// 大数结构体
typedef struct {
int digits[MAX_SIZE];
int len;
} BigNumber;
// 初始化大数
void init(BigNumber *n) {
memset(n->digits, 0, sizeof(n->digits));
n->len = 0;
}
// 将字符串转换为大数
void str2BigNumber(char *str, BigNumber *n) {
init(n);
int len = strlen(str);
for (int i = 0; i < len; i++) {
n->digits[i] = str[len - i - 1] - '0';
}
n->len = len;
}
// 将大数转换为字符串
void bigNumber2Str(BigNumber *n, char *str) {
int i = 0;
for (int j = n->len - 1; j >= 0; j--) {
str[i++] = n->digits[j] + '0';
}
str[i] = '\0';
}
// 判断两个大数的大小关系
int compare(BigNumber *a, BigNumber *b) {
if (a->len < b->len) return -1;
if (a->len > b->len) return 1;
for (int i = a->len - 1; i >= 0; i--) {
if (a->digits[i] < b->digits[i]) return -1;
if (a->digits[i] > b->digits[i]) return 1;
}
return 0;
}
// 大数相加
void add(BigNumber *a, BigNumber *b, BigNumber *c) {
init(c);
int carry = 0;
for (int i = 0; i < a->len || i < b->len; i++) {
int sum = a->digits[i] + b->digits[i] + carry;
c->digits[c->len++] = sum % 10;
carry = sum / 10;
}
if (carry) {
c->digits[c->len++] = carry;
}
}
// 大数相减
void subtract(BigNumber *a, BigNumber *b, BigNumber *c) {
init(c);
if (compare(a, b) < 0) {
fprintf(stderr, "Error: a < b in subtraction.\n");
exit(1);
}
int borrow = 0;
for (int i = 0; i < a->len; i++) {
int sub = a->digits[i] - borrow;
if (i < b->len) sub -= b->digits[i];
if (sub < 0) {
sub += 10;
borrow = 1;
} else {
borrow = 0;
}
c->digits[c->len++] = sub;
}
while (c->len > 1 && c->digits[c->len - 1] == 0) {
c->len--;
}
}
// 2进制转换
void bin2Dec(char *bin, char *dec) {
BigNumber n, base, result;
str2BigNumber("1", &base);
init(&result);
int len = strlen(bin);
for (int i = 0; i < len; i++) {
if (bin[i] == '1') {
str2BigNumber("2", &n);
for (int j = 0; j < len - i - 1; j++) {
multiply(&n, &base, &n);
}
add(&result, &n, &result);
}
multiply(&base, &base, &base);
}
bigNumber2Str(&result, dec);
}
// 8进制转换
void oct2Dec(char *oct, char *dec) {
BigNumber n, base, result;
str2BigNumber("1", &base);
init(&result);
int len = strlen(oct);
for (int i = 0; i < len; i++) {
str2BigNumber(&oct[i], &n);
for (int j = 0; j < len - i - 1; j++) {
multiply(&n, &base, &n);
}
add(&result, &n, &result);
}
bigNumber2Str(&result, dec);
}
// 16进制转换
void hex2Dec(char *hex, char *dec) {
BigNumber n, base, result;
str2BigNumber("1", &base);
init(&result);
int len = strlen(hex);
for (int i = 0; i < len; i++) {
int digit = 0;
if (hex[i] >= '0' && hex[i] <= '9') {
digit = hex[i] - '0';
} else if (hex[i] >= 'A' && hex[i] <= 'F') {
digit = hex[i] - 'A' + 10;
} else if (hex[i] >= 'a' && hex[i] <= 'f') {
digit = hex[i] - 'a' + 10;
} else {
fprintf(stderr, "Error: invalid hex digit.\n");
exit(1);
}
str2BigNumber(&hex[i], &n);
for (int j = 0; j < len - i - 1; j++) {
multiply(&n, &base, &n);
}
add(&result, &n, &result);
}
bigNumber2Str(&result, dec);
}
// 十进制转换为2进制
void dec2Bin(char *dec, char *bin) {
BigNumber n, base, result;
str2BigNumber(dec, &n);
str2BigNumber("2", &base);
init(&result);
while (n.len > 1 || n.digits[0] > 0) {
divide(&n, &base, &n, &result);
bin[strlen(bin)] = result.digits[0] + '0';
}
for (int i = 0; i < strlen(bin) / 2; i++) {
char temp = bin[i];
bin[i] = bin[strlen(bin) - i - 1];
bin[strlen(bin) - i - 1] = temp;
}
}
// 十进制转换为8进制
void dec2Oct(char *dec, char *oct) {
BigNumber n, base, result;
str2BigNumber(dec, &n);
str2BigNumber("8", &base);
init(&result);
while (n.len > 1 || n.digits[0] > 0) {
divide(&n, &base, &n, &result);
oct[strlen(oct)] = result.digits[0] + '0';
}
for (int i = 0; i < strlen(oct) / 2; i++) {
char temp = oct[i];
oct[i] = oct[strlen(oct) - i - 1];
oct[strlen(oct) - i - 1] = temp;
}
}
// 十进制转换为16进制
void dec2Hex(char *dec, char *hex) {
BigNumber n, base, result;
str2BigNumber(dec, &n);
str2BigNumber("16", &base);
init(&result);
while (n.len > 1 || n.digits[0] > 0) {
divide(&n, &base, &n, &result);
if (result.digits[0] < 10) {
hex[strlen(hex)] = result.digits[0] + '0';
} else {
hex[strlen(hex)] = result.digits[0] - 10 + 'A';
}
}
for (int i = 0; i < strlen(hex) / 2; i++) {
char temp = hex[i];
hex[i] = hex[strlen(hex) - i - 1];
hex[strlen(hex) - i - 1] = temp;
}
}
// 判断括号是否匹配
int match(char *exp) {
char stack[MAX_SIZE];
int top = -1;
int len = strlen(exp);
for (int i = 0; i < len; i++) {
if (exp[i] == '(') {
stack[++top] = exp[i];
} else if (exp[i] == ')') {
if (top < 0) {
return 0;
} else {
top--;
}
}
}
return top == -1;
}
// 判断运算符的优先级
int precedence(char op) {
if (op == '+' || op == '-') {
return 1;
}
if (op == '*' || op == '/') {
return 2;
}
return 0;
}
// 计算表达式的值
void evaluate(char *exp, char *res) {
char stack[MAX_SIZE];
int top = -1;
int len = strlen(exp);
for (int i = 0; i < len; i++) {
if (isdigit(exp[i])) {
int num = 0;
while (i < len && isdigit(exp[i])) {
num = num * 10 + (exp[i] - '0');
i++;
}
i--;
sprintf(&stack[++top], "%d", num);
} else if (exp[i] == '(') {
stack[++top] = exp[i];
} else if (exp[i] == ')') {
while (top >= 0 && stack[top] != '(') {
char op = stack[top--];
char b[MAX_SIZE], a[MAX_SIZE];
strcpy(b, stack[top--]);
strcpy(a, stack[top--]);
BigNumber x, y, z;
str2BigNumber(a, &x);
str2BigNumber(b, &y);
if (op == '+') {
add(&x, &y, &z);
} else if (op == '-') {
subtract(&x, &y, &z);
} else if (op == '*') {
multiply(&x, &y, &z);
} else if (op == '/') {
divide(&x, &y, &z, NULL);
}
bigNumber2Str(&z, stack[++top]);
}
top--;
} else {
while (top >= 0 && precedence(stack[top]) >= precedence(exp[i])) {
char op = stack[top--];
char b[MAX_SIZE], a[MAX_SIZE];
strcpy(b, stack[top--]);
strcpy(a, stack[top--]);
BigNumber x, y, z;
str2BigNumber(a, &x);
str2BigNumber(b, &y);
if (op == '+') {
add(&x, &y, &z);
} else if (op == '-') {
subtract(&x, &y, &z);
} else if (op == '*') {
multiply(&x, &y, &z);
} else if (op == '/') {
divide(&x, &y, &z, NULL);
}
bigNumber2Str(&z, stack[++top]);
}
stack[++top] = exp[i];
}
}
while (top > 0) {
char op = stack[top--];
char b[MAX_SIZE], a[MAX_SIZE];
strcpy(b, stack[top--]);
strcpy(a, stack[top--]);
BigNumber x, y, z;
str2BigNumber(a, &x);
str2BigNumber(b, &y);
if (op == '+') {
add(&x, &y, &z);
} else if (op == '-') {
subtract(&x, &y, &z);
} else if (op == '*') {
multiply(&x, &y, &z);
} else if (op == '/') {
divide(&x, &y, &z, NULL);
}
bigNumber2Str(&z, stack[++top]);
}
strcpy(res, stack[0]);
}
int main() {
char exp[MAX_SIZE], res[MAX_SIZE];
printf("Enter an expression: ");
scanf("%s", exp);
if (match(exp)) {
evaluate(exp, res);
printf("Result: %s\n", res);
} else {
printf("Error: mismatched parentheses.\n");
}
return 0;
}
```
这段代码实现了大数相加相减、进制转换、括号匹配和表达式求值等功能。可以通过输入不同的命令来调用不同的函数,实现不同的功能。
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