Basic exercise of test questions hexadecimal to decimal

Resource constraints

The time limit ：1.0s Memory limit ：512.0MB

Problem description

　　 Enter a number from the keyboard that does not exceed 8 A string of positive hexadecimal digits of , Convert it to a positive decimal number and output .
　　 notes ： In hexadecimal numbers 10~15 Use capital letters respectively A、B、C、D、E、F Express .

The sample input

FFFF

Sample output

65535

Topic analysis ：

1. Test binary conversion

2.16 turn 10 Into the system for ：

From the end, it is recorded as 0,s[i]*pow(16,0);

Add one from the end as 1,s[i]*pow(16,1);

And so on

The code is as follows ：

C Language ：

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

int main() {
	char s[8];
	scanf("%s", s);
	long long int sum = 0;
	int top = 0, last = strlen(s) - 1, i;
	for (i = last; i >= 0; i--, top++) {
		if (s[i] == 'A') {
			sum += 10 * pow(16, top);
		} else if (s[i] == 'B') {
			sum += 11 * pow(16, top);
		} else if (s[i] == 'C') {
			sum += 12 * pow(16, top);
		} else if (s[i] == 'D') {
			sum += 13 * pow(16, top);
		} else if (s[i] == 'E') {
			sum += 14 * pow(16, top);
		} else if (s[i] == 'F') {
			sum += 15 * pow(16, top);
		} else if (s[i] - '0' <= 9)
			sum += (s[i] - '0') * pow(16, top);
	}
	printf("%ld", sum);
}

C++:

#include <iostream>
#include <math.h>
using namespace std;

int main() {
	string s;
	cin >> s;
	long long int sum = 0;
	int top = 0, last = s.length() - 1;
	for (int i = last; i >= 0; i--, top++) {
		if (s[i] == 'A') {
			sum += 10 * pow(16, top);
		} else if (s[i] == 'B') {
			sum += 11 * pow(16, top);
		} else if (s[i] == 'C') {
			sum += 12 * pow(16, top);
		} else if (s[i] == 'D') {
			sum += 13 * pow(16, top);
		} else if (s[i] == 'E') {
			sum += 14 * pow(16, top);
		} else if (s[i] == 'F') {
			sum += 15 * pow(16, top);
		} else if (s[i] - '0' <= 9)
			sum += (s[i] - '0') * pow(16, top);
	}
	cout << sum;
}