Title description:
It is worth noting that the decimal system is 0 1 2 3 4 5 6 7 8 9; the binary system is 0 1.
In the question, 1 corresponds to A, 2 corresponds to B...26 corresponds to Z, starting from 1, not 0. Therefore, a minus one operation is required.
Mainly 1-26 is a single letter, 27-+~ is multiple letters (at least two, and starting from AA), code two I took this as a breakthrough point, I tried it twice before writing it correctly, the first time ZY is not handled properly, and AnullY is output, which is a carry problem.
Code two is made with HashMap, code one is ASCII code.
PS: I feel that HashMap understands the meaning of the question better
Code one:
class Solution {
public String convertToTitle(int n) {
StringBuilder sb = new StringBuilder();
while(n>0){
n--;
sb.append((char) ('A' + n % 26));
n = n / 26;
}
return sb.reverse().toString();
}
}
result:
Code two (HashMap):
class Solution {
public String convertToTitle(int n) {
HashMap<Integer,Character> map = new HashMap<Integer,Character>();
int c = 0;
for(char i = 'A';i <= 'Z';i++){
map.put(c++,i);
}
StringBuilder sb = new StringBuilder();
if(n <= 26){
sb.append(map.get(n-1));
}else{
while(n>0){
n--;
sb.append(map.get(n % 26));
n = n / 26;
}
}
return sb.reverse().toString();
}
}
result:
