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109 lines
3.7 KiB
C++
109 lines
3.7 KiB
C++
///////////////////////////////////////////////////////////////////////
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// File: sorthelper.h
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// Description: Generic sort and maxfinding class.
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// Author: Ray Smith
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// Created: Thu May 20 17:48:21 PDT 2010
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//
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// (C) Copyright 2010, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_CCUTIL_SORTHELPER_H_
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#define TESSERACT_CCUTIL_SORTHELPER_H_
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#include <stdlib.h>
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#include "genericvector.h"
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// Generic class to provide functions based on a <value,count> pair.
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// T is the value type.
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// The class keeps a count of each value and can return the most frequent
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// value or a sorted array of the values with counts.
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// Note that this class uses linear search for adding. It is better
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// to use the STATS class to get the mode of a large number of values
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// in a small space. SortHelper is better to get the mode of a small number
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// of values from a large space.
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// T must have a copy constructor.
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template <typename T>
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class SortHelper {
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public:
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// Simple pair class to hold the values and counts.
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template<typename PairT> struct SortPair {
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PairT value;
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int count;
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};
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// qsort function to sort by decreasing count.
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static int SortPairsByCount(const void* v1, const void* v2) {
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const SortPair<T>* p1 = static_cast<const SortPair<T>*>(v1);
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const SortPair<T>* p2 = static_cast<const SortPair<T>*>(v2);
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return p2->count - p1->count;
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}
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// qsort function to sort by decreasing value.
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static int SortPairsByValue(const void* v1, const void* v2) {
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const SortPair<T>* p1 = static_cast<const SortPair<T>*>(v1);
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const SortPair<T>* p2 = static_cast<const SortPair<T>*>(v2);
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if (p2->value - p1->value < 0) return -1;
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if (p2->value - p1->value > 0) return 1;
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return 0;
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}
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// Constructor takes a hint of the array size, but it need not be accurate.
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explicit SortHelper(int sizehint) {
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counts_.reserve(sizehint);
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}
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// Add a value that may be a duplicate of an existing value.
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// Uses a linear search.
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void Add(T value, int count) {
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// Linear search for value.
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for (int i = 0; i < counts_.size(); ++i) {
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if (counts_[i].value == value) {
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counts_[i].count += count;
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return;
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}
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}
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SortPair<T> new_pair = {value, count};
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counts_.push_back(SortPair<T>(new_pair));
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}
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// Returns the frequency of the most frequent value.
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// If max_value is not nullptr, returns the most frequent value.
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// If the array is empty, returns -INT32_MAX and max_value is unchanged.
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int MaxCount(T* max_value) const {
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int best_count = -INT32_MAX;
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for (int i = 0; i < counts_.size(); ++i) {
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if (counts_[i].count > best_count) {
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best_count = counts_[i].count;
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if (max_value != nullptr)
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*max_value = counts_[i].value;
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}
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}
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return best_count;
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}
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// Returns the data array sorted by decreasing frequency.
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const GenericVector<SortPair<T> >& SortByCount() {
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counts_.sort(&SortPairsByCount);
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return counts_;
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}
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// Returns the data array sorted by decreasing value.
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const GenericVector<SortPair<T> >& SortByValue() {
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counts_.sort(&SortPairsByValue);
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return counts_;
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}
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private:
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GenericVector<SortPair<T> > counts_;
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};
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#endif // TESSERACT_CCUTIL_SORTHELPER_H_.
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