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Leetcode#127 Word Ladder

原题地址

 

BFS

Word Ladder II的简化版(参见这篇文章)

由于只需要计算步数,所以简单许多。

 

代码:

 1 int ladderLength(string start, string end, unordered_set<string> &dict) { 2         if (start == end) 3             return 0; 4              5         unordered_set<string> old; 6         queue<string> layer; 7         int len = 1; 8          9         layer.push(start);10         while (!layer.empty()) {11             queue<string> nextLayer;12             while (!layer.empty()) {13                 string str = layer.front();14                 layer.pop();15                 if (str == end)16                     return len;17                 for (int i = 0; i < str.length(); i++) {18                     for (char j = a; j <= z; j++) {19                         string next = str;20                         next[i] = j;21                         if (old.find(next) == old.end() && dict.find(next) != dict.end()) {22                             old.insert(next);23                             nextLayer.push(next);24                         }25                     }26                 }27             }28             len++;29             layer = nextLayer;30         }31         32         return 0;33 }

 

Leetcode#127 Word Ladder