Satisfiability of Equality Equations - LeetCode
阿新 • • 發佈:2019-02-12
toc 字母 應用 www ali 屬於 alt tps map
目錄
- 題目鏈接
- 註意點
- 解法
- 小結
題目鏈接
Satisfiability of Equality Equations - LeetCode
註意點
- 必須要初始化pre
解法
解法一:典型的並查集算法應用。先遍歷所有等式,將等號兩邊的字母加入同一分類,每類中的字母都是相等的。然後遍歷不等式,如果不等號兩邊的字母屬於同一類則返回false。時間復雜度O(nm)
class Solution { public: map<char,char> pre; char Find(char x) { char r = x; while(pre[r] != r) { r = pre[r]; } return r; } void Join(char x,char y) { char fx = Find(x); char fy = Find(y); if(fx != fy) pre[fx] = fy; } void Init() { char letter[26] ={'a','b','c','d','e','f','g','h','i', 'j','k','l','m','n','o','p','q','r', 's','t','u','v','w','x','y','z'}; for (auto l:letter) { pre[l] = l; } } bool equationsPossible(vector<string>& equations) { Init(); for(auto e:equations) { if(e[1] == '=') Join(e[0],e[3]); } for(auto e:equations) { if(e[1] == '!' && Find(e[0]) == Find(e[3])) { return false; } } return true; } };
小結
- 快速搞定並查集算法
Satisfiability of Equality Equations - LeetCode