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440.java
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440.java
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public class Solution {
int [] util(int n) {
List<Integer> res = new ArrayList<>();
while(n > 0) {
res.add(n % 10);
n /= 10;
}
Collections.reverse(res);
int [] ret = new int[res.size()];
for(int i = 0; i< ret.length; ++i)
ret[i] = res.get(i);
return ret;
}
int eq(int [] det, int [] ret, int index) {
for(int i = 0; i<= index; ++i) {
if(det[i] == ret[i]) {
continue;
}
if(det[i] > ret[i]) return -1;
else return 1;
}
return 0;
}
int gen(int wei) {
int ret = 0;
for(int i = 0; i< wei; ++i) {
ret = ret * 10 + 1;
}
return ret;
}
public int findKthNumber(int n, int k) {
int[] det = util(n);
int[] ret = new int[det.length];
int index = 0;
ret[0] = 1;
while(k > 1) {
int com = eq(det, ret, index);
if(com == 0) {
int total = gen(ret.length - index - 1);
int diff = 0;
for(int i = index + 1; i< ret.length; ++i) {
diff = diff * 10 + det[i];
}
total += diff + 1;
if(k - total <= 0 ) {
k --; // skip current one
index++;
//System.out.println(k + " : " + index + " : " + total);
ret[index] = 0;
continue;
}
k -= total;
ret[index] ++;
} else {
int len = (com < 0)?ret.length - index :ret.length - index -1;
int total = gen(len);
if(k - total <= 0 ) {
k --; // skip current one
index++;
ret[index] = 0;
continue;
}
k -= total;
ret[index] ++;
}
}
int res = 0;
for(int i =0; i<= index; ++i) {
res = res * 10 + ret[i];
}
return res;
}
}