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793.cpp
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793.cpp
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__________________________________________________________________________________________________
sample 4 ms submission
class Solution {
public:
int preimageSizeFZF(int K) {
long long l = K, r = 5LL * (long long) K;
while (l <= r) {
long long mid = l + (r - l) / 2;
long long k = count(mid);
// cout<<"count: "<<mid<<"="<<k<<endl;
if (k == K) {
return 5;
} else if (k < K) {
l = mid + 1;
} else {
r = mid - 1;
}
}
return 0;
}
long long count(long long N) {
long long res = 0;
while (N) {
N /= 5;
res += N;
}
return res;
}
};
__________________________________________________________________________________________________
sample 8248 kb submission
class Solution {
private:
bool search(int target, int l, int r, int (*a)(int n)) {
if (a(l) == target || a(r) == target)
return true;
int m;
while (l + 1 < r) {
m = l + (r - l)/2;
if (a(m) == target)
return true;
if (a(m) < target)
l = m;
else
r = m;
}
return false;
}
public:
int preimageSizeFZF(int K) {
auto f = [](int n){
int result = n;
while (n > 0) {
result += n/5;
n /= 5;
}
return result;
};
return (search(K, 0, K, f))? 5 : 0;
}
};
__________________________________________________________________________________________________