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xINFERNOx's blog

Time Complexity Variation

By xINFERNOx, history, 3 years ago, In English

Why the second code executes within 500ms whereas the first one gives TLE(2000ms) ?

1497E1 - Square-Free Division (easy version)

const int N = 1e7 + 5;
vector<int> maping(N);
int i,j;

Code 1

for (i = 1; i < N; i++) {
	maping[i] = i;
}
for (i = 2; i < N; i++) {
  for (j = 2; j * j <= i; j++) {
	 while (maping[i] % (j * j) == 0) maping[i] = maping[i] / (j * j);
	}
}

Code 2

for (i = 1 ; i < N ; i++) maping[i]  = i;
for (i = 2; i < N; i++) {
	for (j = i * i; j <= N; j += i * i) {
		while (maping[j] % (i * i) == 0) {
			maping[j] = maping[j] / (i * i);
		}
	}
}

Full text and comments »

number theory, sieve of eratosthenes, #sieve, doubt

-7

xINFERNOx
3 years ago
3