题目：给定一些无序区间，判断某个给定的特定区间是否在这些无序的区间内。这个题目比较简单，首先将给定的区间排序，在对重合的区间进行排序，使得区间变成递增且不重叠的若干个区间，对于给定的区间在已经处理好的区间内进行二分查找，完成区间覆盖的判断。代码如下：
#include <stdio.h> #include <vector> #include <algorithm> using namespace std; class Interval { public: Interval(int start, int end) : start_(start), end_(end) {} Interval() :start_(0), end_(0) {} static bool OrderByStart(const Interval& left, const Interval& right) { return left.start_ < right.start_; } friend bool operator<(const Interval& left, const Interval& right) { return left.start_ < right.start_; } int start_; int end_; }; void CombinInterval(std::vector<Interval>& orginal, std::vector<Interval>* combined) { if (orginal.size() < 1) { return; } sort(orginal.begin(), orginal.end(), Interval::OrderByStart);//直接使用sort函数进行排序，根据区间的第一个数字大小进行排序 Interval combined_interval = orginal0]; int new_ending = orginal[0].end_; for (int i = 1; i < orginal.size(); ++i) { if (combined_interval.end_ >= orginal[i].start_) { new_ending = combined_interval.end_ > orginal[i].end_ ? combined_interval.end_ : orginal[i].end_; continue; } combined_interval.end_ = new_ending; combined->push_back(combined_interval); combined_interval = orginal[i]; new_ending = orginal[i].end_; } combined_interval.end_ = new_ending; combined->push_back(combined_interval); } bool CoverTest(const Interval& interval, std::vector<Interval>& intervals, Interval* covered_interval) { std::vector<Interval> combined_intervals; CombinInterval(intervals, &combined_intervals); //对原有的区间进行合并 for (int i = 0; i < combined_intervals.size(); ++i) { printf("%d-%d\n", combined_intervals[i].start_, combined_intervals[i].end_); } if (combined_intervals.size() < 1) { return false; } int start = 0; int end = combined_intervals.size() -1; int middle = 0; bool found = false; while (end >= start) { middle = (start + end) / 2; if (interval < combined_intervals[middle]) //在类中定义了类的<操作 { end = middle - 1; } else if (combined_intervals[middle] < interval) { start = middle + 1; } else { found = true; break; } } int target_index = found ? middle : start - 1; printf("target:%d\n", target_index); if (target_index >= 0 && combined_intervals[target_index].start_ <= interval.start_ && combined_intervals[target_index].end_ >= interval.end_) { *covered_interval = combined_intervals[target_index]; return true; } else { return false; } } int main(int argc, char** argv) { std::vector<Interval> intervals; intervals.push_back(Interval(2,5)); intervals.push_back(Interval(3,4)); intervals.push_back(Interval(4,7)); intervals.push_back(Interval(9,13)); Interval target_interval(3, 4); Interval covered_interval; //判断出重合区间 if (CoverTest(target_interval, intervals, &covered_interval)) { printf("the covered interval is (%d, %d)\n", covered_interval.start_, covered_interval.end_); } else { printf("uncovered\n"); } return 0; }
