位操作，插入，二進制

Question

我不確定爲什麼某些代碼格式不正確，所以如果難以閱讀，我很抱歉。我正在爲我的一個課程學習C++，但我被卡住了。我對這門語言知之甚少，所以我實在不知道接下來會發生什麼問題或做什麼。

該程序應該採用四個參數，一個二進制數，一個第二個二進制數，一個位置編號和來自新編號的位數。它應該從新的號碼中取出第一個（位數），並將它們插入原始位置（短）。

目標是讓底部的測試通過。我設法刪除所有的錯誤消息，但測試沒有通過，所以我必須在某處發生邏輯錯誤。

#include <iostream> 
#include <cassert> 
#include <bitset> 
#include <climits> 
using namespace std; 

    // Return the altered bits of "input" 
// where the first "numBits" of "newBits" (unspecified bits are 0) 
// replace "input" bits starting at "position" 

unsigned char set_bits_to(
    unsigned char input, 
    unsigned char newBits, 
    short position, 
    short numBits){ 
//Your Code Here 

    unsigned char insert; 
    int x; 
    int i; 
    int q = 0; 

    if (input < 225) { 
     bitset<4> o(input); 
     bitset<4> d(newBits); 


     for (x = 0; x < numBits; x++) { 
      insert = o[position] = d[q]; 
      q++; 
      position = position + 1; 
     } 

    } 


    // else { 
    //  bitset<8> x(input); 
    // }(input) 
    //bitset<8> x(input); 



    //Stop Code Here   
}; 

int main() { 

    assert(set_bits_to(0b1111, 0b0, 0, 1) == 0b1110); 
    assert(set_bits_to(0b1111, 0b0, 1, 1) == 0b1101); 
    assert(set_bits_to(0b1111, 0b0, 0, 3) == 0b1000); 

    assert(set_bits_to(0b11001100, 0b101, 2, 3) == 0b11010100); 
    assert(set_bits_to(0b11001100, 0b101, 2, 5) == 0b10010100); 
    assert(set_bits_to(0b11001100, 0b101, 3, 3) == 0b11101100); 
    assert(set_bits_to(0b11001100, 0b101, 5, 3) == 0b10101100); 

    assert(set_bits_to(0b1111, 0b101010, 0, 6) == 0b101010); 
    assert(set_bits_to(0b1111, 0b101010, 1, 6) == 0b1010101); 
    assert(set_bits_to(0b1111, 0b101010, 0, 3) == 0b1010); 

    cout << "All tests passed" << endl; 
    return 0; 
} 

Answer 1

這裏是我的解決方案：

char insert = (~0 << numOfBits) & newBits; // these bits would be inserted 
// this piece of code cleans bits between position and position - numOfBits 
char positioned = ((~0 << position) | // preserves bits from position to MSB 
    ~(~0 << (position - numOfBits)) // preservs bits from position to LSB 
     & input; 
input = positioned & insert << position;