从字符串中提取数字并排序输出

 

 

从字符串中提取数字并排序输出

 

看到别人的讨论贴，也做了下。题目很简单，可以直接用标准库函数，也可以自已造轮子。标准库中能用到的只有：atoi / strtol系列，显然得用 strtol（有些库atoi就是用strtol实现的）

在用strtol前，先要对不安全的strtol封装下。

 

int str2i(const char str[], const char* &next, int base = 10)

{

  return strtol(str, const_cast<char**>(&next), base);

}

 

可采用两种算法：

  1 先忽略空白字符，然后直接调用str2i （代码 solve1）

  2 先找到合法数字的第一个字符，再调用str2i（代码 solve2）

当然也可以自行实现strtol（代码： solve3和solve4）。

 

 

// http://cnblogs.com/flyinghearts
#include <iostream>
#include <algorithm>
#include <iterator>
#include <deque>
#include <limits>
#include <cstdlib>
using std::cout;

int str2i(const char str[], const char* &next, int base = 10)
{
  return strtol(str, const_cast<char**>(&next), base);
}

void solve1(const char* str)
{
  if (str == NULL) return;
  std::deque<int> dq;
  const char* p = str;
  const char* next = NULL;
  
  while (*p) {
    if (isspace(*p)) {
      ++p;
      continue;
    }
    errno = 0;
    int value = str2i(p, next);  
    if (errno != 0) { 
      cout << "data error at pos: " << p - str << "\n"; 
      p = next;
      continue; 
    }
    if (next > p) {
      p = next;
      dq.push_back(value);   
      continue;      
    }
    ++p;
  }
  
  std::sort(dq.begin(), dq.end());
  std::copy(dq.begin(), dq.end(), std::ostream_iterator<int>(cout," ")); 
  cout << "\n\n";
}


void solve2(const char* str)
{
  if (str == NULL) return;
  std::deque<int> dq;
  const char* p = str;
  const char* next = NULL;
  
  while (*p) {
    if (!isdigit(*p) && (*p != '-' || !isdigit(*(p + 1)))) {
      ++p;
      continue;
    }
    
    errno = 0;
    int value = str2i(p, next);
    if (errno != 0) { 
      cout << "data error at pos: " << p - str << "\n"; 
      p = next;
      continue; 
    }
    if (next > p) {
      p = next;
      dq.push_back(value);     
    }
  }
  
  std::sort(dq.begin(), dq.end());
  std::copy(dq.begin(), dq.end(), std::ostream_iterator<int>(std::cout," ")); 
  cout << "\n\n";
}




void solve3(const char* str)
{
  //const int max_int = -1u / 2u;
  const int max_int = std::numeric_limits<int>::max();
  const int max_value = max_int / 10;
  const int value_left = max_int % 10;
  
  const char* p = str;
  std::deque<int> dq;
  
  while (*p) {
    while (*p == ' ' || *p == '\t') ++p;
    bool negative = false;
    if (*p == '-') { negative = true; ++p; }
    else if (*p == '+') { ++p; }
        
    int value = 0;
    bool range_error = false;
    bool value_read = false;
    const char *old = p;
    for ( ; *p; ++p) {
      int tmp = *p - '0';
      if (tmp < 0 || tmp > 9) break;
      if (range_error) continue;
      if (value > max_value || (value == max_value && tmp > value_left + negative)) {
        range_error = true;
        continue;
      }
      value = value * 10 + tmp;
      value_read = true;
    }
    
    if (range_error) {
      cout << "data error at pos: " << old - str << "\n"; 
      continue;
    } 
       
    if (value_read) {
      if (negative) value = - value; 
      dq.push_back(value);
    }
    
    if (*p == 0) break; 
    ++p;    
  }
  
  std::sort(dq.begin(), dq.end());
  std::copy(dq.begin(), dq.end(), std::ostream_iterator<int>(std::cout," ")); 
  cout << "\n\n";
  
}


void solve4(const char* str)
{
  //const int max_int = -1u / 2u;
  const int max_int = std::numeric_limits<int>::max();
  const int max_value = max_int / 10;
  const int value_left = max_int % 10;
  
  const char* p = str;
  std::deque<int> dq;
  
  bool negative = false;
  while (*p) {           
    if (!isdigit(*p)) { 
      if (*p++ != '-' ) continue; 
      if (!isdigit(*p)) continue;
      negative = true;
    }
    
    const char *old = p;
    int value = *p++ - '0';
    bool range_error = false;
    for ( ; *p; ++p) {
      if (!isdigit(*p)) break;
      if (range_error) continue;
      int tmp = *p - '0';
      if (value > max_value || (value == max_value && tmp > value_left + negative)) {
        range_error = true;
        continue;
      }
      value = value * 10 + tmp;
    }
    
    if (range_error) {
      cout << "data error at pos: " << old - str << "\n"; 
      continue;
    } 
    
    if (negative) {
      value = - value; 
      negative = false;
    }
    
    dq.push_back(value);    
    if (*p == 0) break;
    ++p; 
  }
  
  std::sort(dq.begin(), dq.end());
  std::copy(dq.begin(), dq.end(), std::ostream_iterator<int>(std::cout," ")); 
  cout << "\n\n";
  
}


int main()
{   
  char ss[] = "2147483646 2147483647 2147483648 -2147483647  -2147483648 -2147483649";   
  char str[] = "-a33k&-99+r5s-w1f10g-2d4vc+511m99999999999999gc3-";
  solve1(str); 
  solve2(str);
  solve3(str);  
  solve4(str); 
  solve1(ss); 
  solve2(ss);
  solve3(ss); 
  solve4(ss);
}