48 lines
883 B
C++
48 lines
883 B
C++
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#include <iostream>
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using namespace std;
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const int maxn = 200000;
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int t[maxn];
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void add(int t[], int i, int value) {
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for (; i < maxn; i |= i + 1)
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t[i] += value;
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}
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// sum[0,i]
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int sum(int t[], int i) {
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int res = 0;
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for (; i >= 0; i = (i & (i + 1)) - 1)
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res += t[i];
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return res;
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}
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// Returns min(p|sum[0,p]>=sum)
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int lower_bound(int t[], int sum) {
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--sum;
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int pos = -1;
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for (int blockSize = 1 << 30; blockSize != 0; blockSize >>= 1) {
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if (blockSize > maxn) continue;
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int nextPos = pos + blockSize;
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if (nextPos < maxn && sum >= t[nextPos]) {
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sum -= t[nextPos];
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pos = nextPos;
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}
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}
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return pos + 1;
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}
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// Usage example
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int main() {
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add(t, 0, 4);
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add(t, 1, 5);
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add(t, 2, 5);
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add(t, 2, 5);
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cout << (4 == sum(t, 0)) << endl;
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cout << (19 == sum(t, 2)) << endl;
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cout << (2 == lower_bound(t, 19)) << endl;
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cout << (maxn == lower_bound(t, 20)) << endl;
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}
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