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# 图 floyd

399. Evaluate Division
Medium

You are given an array of variable pairs `equations` and an array of real numbers `values`, where `equations[i] = [Ai, Bi]` and `values[i]` represent the equation `Ai / Bi = values[i]`. Each `Ai` or `Bi` is a string that represents a single variable.

You are also given some `queries`, where `queries[j] = [Cj, Dj]` represents the `jth` query where you must find the answer for `Cj / Dj = ?`.

Return the answers to all queries. If a single answer cannot be determined, return `-1.0`.

Note: The input is always valid. You may assume that evaluating the queries will not result in division by zero and that there is no contradiction.

Example 1:

```Input: equations = [["a","b"],["b","c"]], values = [2.0,3.0], queries = [["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]
Output: [6.00000,0.50000,-1.00000,1.00000,-1.00000]
Explanation:
Given: a / b = 2.0, b / c = 3.0
queries are: a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ?
return: [6.0, 0.5, -1.0, 1.0, -1.0 ]
```

Example 2:

```Input: equations = [["a","b"],["b","c"],["bc","cd"]], values = [1.5,2.5,5.0], queries = [["a","c"],["c","b"],["bc","cd"],["cd","bc"]]
Output: [3.75000,0.40000,5.00000,0.20000]
```

Example 3:

```Input: equations = [["a","b"]], values = [0.5], queries = [["a","b"],["b","a"],["a","c"],["x","y"]]
Output: [0.50000,2.00000,-1.00000,-1.00000] ```

Constraints:

• `1 <= equations.length <= 20`
• `equations[i].length == 2`
• `1 <= Ai.length, Bi.length <= 5`
• `values.length == equations.length`
• `0.0 < values[i] <= 20.0`
• `1 <= queries.length <= 20`
• `queries[i].length == 2`
• `1 <= Cj.length, Dj.length <= 5`
• `Ai, Bi, Cj, Dj` consist of lower case English letters and digits.
```class Solution {
public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
Map<String,Map<String,Double>> map = new HashMap();

for(int i=0;i<values.length;i++){
String first = equations.get(i).get(0),second = equations.get(i).get(1);
map.put(first,map.getOrDefault(first,new HashMap()));
map.put(second,map.getOrDefault(second,new HashMap()));
Map<String,Double> firstMap = map.get(first);
Map<String,Double> secondMap = map.get(second);
firstMap.put(first,1d);
secondMap.put(second,1d);
firstMap.put(second,values[i]);
secondMap.put(first,1/values[i]);
}
for(String key:map.keySet()){
Map<String,Double> currmap = map.get(key);
for(String key1:currmap.keySet()){
for(String key2:currmap.keySet()){
if(key.equals(key1) || key.equals(key2) || key1.equals(key2)) continue;
double value12 = map.get(key1).get(key)/map.get(key2).get(key);
map.get(key1).put(key2,value12);
map.get(key2).put(key1,1/value12);
}
}
}
double[] results = new double[queries.size()];
for(int i=0;i<queries.size();i++){
String first = queries.get(i).get(0),second = queries.get(i).get(1);
if(map.get(first)!=null && map.get(first).get(second)!=null)
results[i]=map.get(first).get(second);
else
results[i]=-1;
}
return results;
}
}```