51 lines
1 KiB
C++
51 lines
1 KiB
C++
#include <cassert>
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namespace {
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long sum(long index, long value, long n) {
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long count = 0;
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if (value > index) {
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count += (2 * value - index) * (index + 1) / 2;
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} else {
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count += (value + 1) * value / 2 + index - value + 1;
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}
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if (value >= n - index) {
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count += (2 * value - n + 1 + index) * (n - index) / 2;
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} else {
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count += (value + 1) * value / 2 + n - index - value;
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}
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return count - value;
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}
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} // namespace
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class Solution {
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public:
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int maxValue(int n, int index, int maxSum) {
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int left = 1, right = maxSum;
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while (left < right) {
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int mid = (left + right + 1) / 2;
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if (sum(index, mid, n) <= maxSum) {
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left = mid;
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} else {
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right = mid - 1;
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}
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}
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return left;
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}
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};
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int main() {
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Solution s;
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assert(s.maxValue(4, 2, 6) == 2);
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assert(s.maxValue(6, 1, 10) == 3);
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// regression
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assert(s.maxValue(6, 2, 931384943) == 155230825);
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return 0;
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}
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