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31 changes: 31 additions & 0 deletions 38. Count and Say
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
class Solution {
public String countAndSay(int n) {
if (n <= 0) {
throw new IllegalArgumentException("Invalid input");
}

StringBuilder sb = new StringBuilder("1");
for (int i = 2; i <= n; i++) {
sb = getNextState(sb);
}
return sb.toString();
}

private StringBuilder getNextState(StringBuilder curSb) {
StringBuilder nextSb = new StringBuilder();
int len = curSb.length();
int i = 0;

while (i < len) {
char c = curSb.charAt(i++);
int count = 1;
while (i < len && c == curSb.charAt(i)) {
count++;
i++;
}
nextSb.append(count).append(c);
}

return nextSb;
}
}