42 lines
1.0 KiB
Plaintext
42 lines
1.0 KiB
Plaintext
//三分 求函数极大值
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const double EPS = 1e-9;
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double TS(double l, double r) {
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while (r - l > EPS) {
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double mid1 = l + (r - l) / 3.0, mid2 = r - (r - l) / 3.0;
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if (calc(mid1) > calc(mid2)) { r = mid2; }
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else { l = mid1; }
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}
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return l;
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}
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//归并排序 求逆序数
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ll cnt;
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void mergeSort(int a[], int l, int r) {
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if (l >= r) { return; }
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int mid = (l + r) >> 1;
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mergeSort(a, l, mid);
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mergeSort(a, mid + 1, r);
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vector<int> res(r - l + 1);
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int i = l, j = mid + 1, k = 0;
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while (i <= mid && j <= r) {
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if (a[i] > a[j]) { res[k++] = a[j++]; cnt += mid + 1 - i; }
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else { res[k++] = a[i++]; }
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}
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while (i <= mid) { res[k++] = a[i++]; }
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while (j <= r) { res[k++] = a[j++]; }
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for (k = l; k <= r; k++) { a[k] = res[k - l]; }
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}
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//快排
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void quickSort(int a[], int l, int r) {
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if (l >= r) { return; }
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int i = l, j = r, v = a[l];
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while (i < j) {
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while (i < j && a[j] >= v) { j--; }
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a[i] = a[j];
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while (i < j && a[i] <= v) { i++; }
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a[j] = a[i];
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}
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a[i] = v;
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quickSort(a, l, i - 1);
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quickSort(a, i + 1, r);
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}
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