自定義排序需要單獨寫一個compare函數
例1 LeetCode 056. Merge Intervals
Given a collection of intervals, merge all overlapping intervals.
For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].
1 /** 2 * Definition for an interval. 3 * struct Interval { 4 * int start; 5 * int end; 6 * Interval() : start(0), end(0) {} 7 * Interval(int s, int e) : start(s), end(e) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 vector<Interval> merge(vector<Interval>& ins) { 13 if (ins.empty()) 14 return vector<Interval>{}; 15 vector<Interval> res; 16 sort(ins.begin(), ins.end(), [](Interval a, Interval b){return a.start < b.start;}); 17 res.push_back(ins[0]); 18 19 for (int i = 1; i < ins.size(); i++) { 20 if (res.back().end < ins[i].start) 21 res.push_back(ins[i]); 22 else 23 res.back().end = max(res.back().end, ins[i].end); 24 } 25 return res; 26 } 27 };
函數寫法：
1 /** 2 * Definition for an interval. 3 * struct Interval { 4 * int start; 5 * int end; 6 * Interval() : start(0), end(0) {} 7 * Interval(int s, int e) : start(s), end(e) {} 8 * }; 9 */ 10 bool mySort(const Interval &a, const Interval &b) { 11 return a.start < b.start; 12 } 13 class Solution { 14 public: 15 vector<Interval> merge(vector<Interval>& ins) { 16 if (ins.empty()) 17 return vector<Interval>{}; 18 vector<Interval> res; 19 sort(ins.begin(), ins.end(), mySort); 20 res.push_back(ins[0]); 21 22 for (int i = 1; i < ins.size(); i++) { 23 if (res.back().end < ins[i].start) 24 res.push_back(ins[i]); 25 else 26 res.back().end = max(res.back().end, ins[i].end); 27 } 28 return res; 29 } 30 };
注意到compare函數寫在類外，這是因為
std::sort要求函數對象，或是靜態/全局函數指針，
非靜態成員函數指針不能直接傳遞給std::sort