C/C++課題ネタ10_文字列の操作

main_23.cpp

//==========
// 数値から文字列への変換
// 1, Compile
//		g++ -std=c++17 -Wall -Wextra main.cpp
// 2, Run
//		./a.out

#include <math.h>
#include <stdio.h>
#include <string>
#include <vector>

using namespace std;

const string CODE = "0123456789ABCDEF";

string n2s(int num){
	string str = "";
	do{
		str = char(CODE[num%16]) + str;
		num = num>>4;
	}while(0 < num);
	return str;
}

int main(){
	printf("Hello, Cpp!!\n");

	// 16進数
	const vector<int> nums = {0x7D, 0xAD, 0xF0, 0x0D};

	for(auto num: nums){
		const string str = n2s(num);
		printf("Num: %d -> Str: %s\n", num, str.c_str());
	}

	return 0;
}

main_24.cpp

//==========
// 文字列から数値への変換
// 1, Compile
//		g++ -std=c++17 -Wall -Wextra main.cpp
// 2, Run
//		./a.out

#include <math.h>
#include <stdio.h>
#include <string>
#include <vector>

using namespace std;

const string CODE = "0123456789ABCDEF";

string n2s(int num){
	string str = "";
	do{
		str = char(CODE[num%16]) + str;
		num = num>>4;
	}while(0 < num);
	return str;
}

unsigned int c2n(const char c){
	if('0' <= c && c <= '9') return c - '0';
	if('A' <= c && c <= 'F') return c - 'A' + 10;
	if('a' <= c && c <= 'f') return c - 'f' + 10;
	return -1;// Error
}

int main(){
	printf("Hello, Cpp!!\n");

	// 文字列
	const vector<string> strs = {"7D", "AD", "F0", "0D"};

	for(auto str: strs){
		unsigned int num = 0;
		for(size_t i=0; i<str.size(); i++){
			num += c2n(str[i]);
			if(i < str.size()-1) num = num<<4;
		}
		printf("Str: %s -> Num: %d -> Str: %s\n", str.c_str(), num, n2s(num).c_str());
	}

	return 0;
}