將數字字符串中的數字轉換爲整數然後將其轉換爲數組

Question

我有一個1000位數字，我將其存儲爲一個字符串。我想以該數字中的每個數字作爲其向量中的元素。所以「12345」將是{1,2,3,4,5}。這是我迄今爲止的代碼，但它不起作用。錯誤來自將字符串字母與數字進行比較。任何幫助，將不勝感激。我看到另一個類似的問題，但字符串中包含數字之間的空格，但這不是。

#include "stdafx.h" 
#include <iostream> 
#include <vector> 
#include <sstream> 
#include <string> 

int main() 
{ 


std::string input_string = "73167176531330624919225119674426574742355349194934" 
"96983520312774506326239578318016984801869478851843" 
"85861560789112949495459501737958331952853208805511" 
"12540698747158523863050715693290963295227443043557" 
"66896648950445244523161731856403098711121722383113" 
"62229893423380308135336276614282806444486645238749" 
"30358907296290491560440772390713810515859307960866" 
"70172427121883998797908792274921901699720888093776" 
"65727333001053367881220235421809751254540594752243" 
"52584907711670556013604839586446706324415722155397" 
"53697817977846174064955149290862569321978468622482" 
"83972241375657056057490261407972968652414535100474" 
"82166370484403199890008895243450658541227588666881" 
"216427171479924442928230863465674813919123162824586" 
"17866458359124566529476545682848912883142607690042" 
"24219022671055626321111109370544217506941658960408" 
"07198403850962455444362981230987879927244284909188" 
"84580156166097919133875499200524063689912560717606" 
"05886116467109405077541002256983155200055935729725" 
"71636269561882670428252483600823257530420752963450"; 

std::cout << "storing string" << std::endl; 

std::vector<int> return_vector; 

for (int i = 0; i<1000; i++) 
{ 
    if (&input_string[i] == "0") 
    { 
     std::cout << 0 << std::endl; 
     return_vector.push_back(0); 
    } 

    if (&input_string[i] == "1") 
    { 
     return_vector.push_back(1); 
    } 

    if (&input_string[i] == "2") 
    { 
     return_vector.push_back(2); 
    } 

    if (&input_string[i] == "3") 
    { 
     return_vector.push_back(3); 
    } 

    if (&input_string[i] == "4") 
    { 
     return_vector.push_back(4); 
    } 

    if (&input_string[i] == "5") 
    { 
     return_vector.push_back(5); 
    } 

    if (&input_string[i] == "6") 
    { 
     return_vector.push_back(6); 
    } 

    if (&input_string[i] == "7") 
    { 
     std::cout << 7 << std::endl; 
     return_vector.push_back(7); 
    } 

    if (&input_string[i] == "8") 
    { 
     return_vector.push_back(8); 
    } 

    if (&input_string[i] == "9") 
    { 
     return_vector.push_back(9); 
    } 




} 

std::cout << "processing string" << std::endl; 


for (int j = 0; j<1000; j++) 
{ 
    std::cout << return_vector[j] << std::endl; 
} 

std::getchar(); 
return 0; 
} 

Answer 1

要列使用比較字符

input_string[i] == '0' 

所以更換

if (&input_string[i] == "0") 

與

if (input_string[i] == '0') //Removed & from &input_string[i], and replace double quotation(") to single quotation('). 

更好的辦法

你不需要批量大小的if-else，您可以像使用

return_vector.reserve(input_string.length()); //Requests vector capacity be at least enough to contain input_string.length() number of element, which reduce redundant reallocation. 

for (int i = 0; i<input_string.length(); i++) 
{ 
    return_vector.push_back(input_string[i]-'0'); 
} 

Answer 2

我們可以用std::transform和lambda做到這一點

std::string test = "123456789"; 
std::vector<int> result(test.size()); 
std::transform(test.begin(), test.end(), result.begin(), [](char ch) { return ch - '0'; }); 

Live Example

Answer 3

您可以在ASCII字符代碼和數字之間進行數學轉換 - 只需減去'0'（即十進制48）：

for (char c : input_string) 
    return_vector.push_back(c - '0'); 

Answer 4

嘗試這種情況：

std::vector<int> toVector(std::string str) 
    { 
     std::vector<int> result(str.size()); 
     std::transform(str.begin(), str.end(), result.begin(), [](char ch){return ch-'0';}); 
     return result; 
    }