我已经尝试了atoi()函数和strtol()函数但没有获得所需的输出。如何将字符串转换为数值,就像输入一千个输出应该是1000。 谢谢
#include<stdio.h>
#include<stdlib.h>
int main ()
{
int i;
char buffer [256];
printf ("Enter a number: ");
fgets (buffer, 256, stdin);
i = atoi (buffer);
printf ("The value entered is %d.",i);
return 0;
}
答案 0 :(得分:1)
用自然语言解析数字并非易事。您可以通过字符串匹配检测小数字,并且通过拆分它们很容易解析像“二十三”这样的数字,但一般的方法很难。例如,“三十万”中的“百”这个词指的是100,000,而不是100。
这没有库函数,因为数字更好,更普遍地表示为十进制数。此外,这样的功能只能用一种语言工作。
但你可以自己动手。下面的代码将单词划分为多个值(例如四,二十三)和乘数(例如千)。两者都是可选的。它保留了一堆这样的价值乘数对来跟踪“优先级”:“一万四千”意味着(1 * 100 + 4) * 1000
,但“一千一百四”意味着1 * 1000 + 1 * 100 + 4
。当第一个乘数小于以下时,首先计算它。
代码区分大小写,但它可以用于字符串文字。一个小型测试套件位于下面的main
函数中。
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>
static const char *next(const char **p, int *len)
{
const char *t = NULL;
while (**p == ' ' || **p == '-') (*p)++;
if (**p == '\0') return NULL;
t = *p;
while (**p && **p != ' ' && **p != '-') (*p)++;
if (len) *len = *p - t;
return t;
}
static int eq(const char *q, const char *p, int len)
{
if (p == NULL) return 0;
while (len--) {
if (*p != *q) return 0;
if (*p == '\0' || *q == '\0') return 0;
p++; q++;
}
return (*q == '\0');
}
static int in(const char **q, const char *p, int len)
{
int ix = 0;
if (p == NULL) return 0;
while (*q) {
if (eq(*q, p, len)) return ix;
ix++;
q++;
}
return -1;
}
#define MAX 32
int parse_num(const char *p, int64_t *n)
{
static const char *ones[] = {
"zero", "one", "two", "three", "four", "five", "six",
"seven", "eight", "nine", "ten", "eleven", "twelve",
"thirteen", "fourteen", "fifteen", "sixteen",
"seventeen", "eighteen", "nineteen", NULL
};
static const char *tens[] = {
"-", "-", "twenty", "thirty", "forty", "fifty",
"sixty", "seventy", "eighty", "ninety", NULL
};
int64_t value[MAX];
int64_t base[MAX];
int nvalue = 0;
const char *t;
int neg = 0;
int len;
int x;
*n = 0;
t = next(&p, &len);
if (eq("minus", t, len)) {
neg = 1;
t = next(&p, &len);
}
while (t) {
int64_t num = 0;
int64_t mult = 1;
int valid = 0;
if (nvalue && eq("and", t, len)) t = next(&p, &len);
x = in(tens, t, len);
if (x >= 0) {
num += x * 10;
t = next(&p, &len);
valid = 1;
}
x = in(ones, t, len);
if (x >= 0) {
num += x;
t = next(&p, &len);
valid = 1;
}
if (valid == 0) {
long int l;
char *end;
l = strtol(t, &end, 10);
if (end == p) {
num = l;
valid = 1;
t = next(&p, &len);
}
}
if (eq("quadrillion", t, len)) mult = 1000000000000000LL;
if (eq("trillion", t, len)) mult = 1000000000000LL;
if (eq("billion", t, len)) mult = 1000000000LL;
if (eq("million", t, len)) mult = 1000000LL;
if (eq("thousand", t, len)) mult = 1000LL;
if (eq("hundred", t, len)) mult = 100LL;
if (mult > 1) {
valid = 1;
t = next(&p, &len);
}
if (valid == 0) return 0;
if (nvalue && base[nvalue - 1] == mult) return 0;
while (nvalue && base[nvalue - 1] < mult) {
nvalue--;
num += value[nvalue] * base[nvalue];
}
if (nvalue == MAX) return 0;
if (mult > 1 && num == 0) num = 1;
value[nvalue] = num;
base[nvalue] = mult;
nvalue++;
}
if (t != NULL) return 0;
if (nvalue == 0) return 0;
while (nvalue--) {
*n += value[nvalue] * base[nvalue];
}
if (neg) *n = -*n;
return 1;
}
int main()
{
const char *str[] = {
"zero",
"three",
"minus one",
"ten",
"twenty-one",
"eighty",
"eight hundred eighty-eight",
"three hundred and nineteen",
"eleven hundred",
"one hundred and twenty one",
"twenty-four thousand",
"thirty thousand one",
"two million",
"two hundred thirty thousand and eleven",
"three million two hundred and thirty thousand and eleven",
"minus eight trillion",
"fifty-five billion one million nine thousand and twelve",
"one thousand million",
"nine hundred thousand",
"nine thousand hundred",
"one hundred thousand million",
"nineteen hundred eighty-four",
"4 billion 294 million 967 thousand 296",
"two thousand thousand",
"minus",
"thirty-something",
NULL
};
const char **p = str;
while (*p) {
int64_t n;
int res;
res = parse_num(*p, &n);
if (res) {
printf("%18" PRId64, n);
} else {
printf("%18s", "---");
}
printf(" %s\n", *p);
p++;
}
return 0;
}
答案 1 :(得分:0)
strtol,atoi仅用于类型转换..他们不知道它的价值是什么。
他们只是将整数599转换为字符串599 ..但不是“五百九十九”
http://www.tutorialspoint.com/c_standard_library/c_function_strtol.htm
http://www.tutorialspoint.com/c_standard_library/c_function_atoi.htm