Topic description : In Microsoft Excel, use A for column 1, B for column 2... Z for column 26, AA for column 27, AB for column 28... and so on. Please write a function, enter the column number in letters, enter the column number it is.
For example: Input: HAT - Output: 5454, Input: AA - Output: 27,
Analysis of the topic : From the requirements of the topic, we need to implement a function that converts the input string into an integer, and this requirement actually requires us to represent the input in hexadecimal (twenty-six represented by A~Z). hexadecimal) strings are converted to decimal.
Analysis of ideas : For example, if we want to convert the hexadecimal ABC into decimal, we do this: A * 26^2 + B * 26^1 + C * 26^0, then we can use this general formula Deduce its general expression: weight(A) * 26^n, weight(A) represents the value represented in hexadecimal, n represents the position of A in the string, n = length - i - 1, i represents the position of the character ch in the string.
Code implementation :
package IQ15;//Interview questions
/**
*
* @author Kang Xi
* Question: In Excel, use A for column 1, B for column 2..., Z for column 26, AA for column 27, AB for column 28..., and so on . Please write a function,
* Enter the column number code represented by letters, and output which column he is.
*
*/
public class Test {
/**
* Convert decimal to hexadecimal (hexadecimal represented by A~Z)
* Here we use the reverse remainder method to convert decimal to hexadecimal
* @param n
* @return
*/
private static StringBuffer DecimalToTwentysix(int n) {
StringBuffer result = new StringBuffer();
while(n > 0) {
int remainder = n % 26;
result.append((char)(remainder + 64));//The ASCII code value of uppercase A is 65
n = n/26;
}
return result.reverse();//String reverse
}
/**
* Convert hexadecimal to decimal
* @param str
* @return
*/
private static int TwentysixToDecimal(String str) {
String strWeight = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
int result = 0;
for(int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
int weight = weight(strWeight, ch);
result += Math.pow(26, str.length()-i-1) * weight;
}
return result;
}
//Return the weight represented by the character ch in str
private static int weight(String str, char ch) {
int weight = 0;
for(int i = 0; i < str.length(); i++) {
if(str.charAt(i) == ch) {
weight = i+1;
}
}
return weight;
}
public static void main(String[] args) {
System.out.println(TwentysixToDecimal("HAT"));
System.out.println(DecimalToTwentysix(5454));
}
}