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440.java
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440.java
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__________________________________________________________________________________________________
sample 0 ms submission
class Solution {
public int findKthNumber(int n, int k) {
int curr = 1;
k = k - 1;
while (k > 0) {
int steps = calSteps(n, curr, curr + 1);
if (steps <= k) {
curr += 1;
k -= steps;
} else {
curr *= 10;
k -= 1;
}
}
return curr;
}
public int calSteps(int n, long n1, long n2) {
int steps = 0;
while (n1 <= n) {
steps += Math.min(n + 1, n2) - n1;
n1 *= 10;
n2 *= 10;
}
return steps;
}
}
__________________________________________________________________________________________________
sample 31588 kb submission
class Solution {
private int nOnes(int n) {
int ans = 0;
while (n-- > 0) {
ans = ans * 10 + 1;
}
return ans;
}
private int digits(int x) {
int ans = 0;
while (x > 0) {
ans++;
x /= 10;
}
return ans;
}
private int pow10(int n) {
int ans = 1;
while (n-- > 0) {
ans *= 10;
}
return ans;
}
private int numStartWith(int n, int x, int pow) {
if (x == 0) {
return 0;
}
int mod = pow10(pow), start = n / mod;
if (start > x) {
return nOnes(pow + 1);
} else {
return nOnes(pow) + (start == x ? n % mod + 1 : 0);
}
}
public int findKthNumber(int n, int k) {
int ans = 0;
for (int i = digits(n) - 1; i >= 0; --i) {
int sum = 0;
for (int j = 0; j < 10; ++j) {
int cur = numStartWith(n, 10 * ans + j, i);
if (sum + cur >= k) {
k -= sum;
ans = 10 * ans + j;
break;
}
sum += cur;
}
if (k == 1) {
break;
} else {
k--;
}
}
return ans;
}
}
__________________________________________________________________________________________________