bfs dfs 399

Author: yiGmMk

go/bfs-dfs/399/399.除法求值.go

@@ -0,0 +1,217 @@
+/*
+* @lc app=leetcode.cn id=399 lang=golang
+*
+* [399] 除法求值
+*
+* https://leetcode.cn/problems/evaluate-division/description/
+*
+  - algorithms
+  - Medium (59.00%)
+  - Likes:    1043
+  - Dislikes: 0
+  - Total Accepted:    86.7K
+  - Total Submissions: 147.1K
+  - Testcase Example:  '[["a","b"],["b","c"]]\n' +
+    '[2.0,3.0]\n' +
+    '[["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]'
+
+*
+* 给你一个变量对数组 equations 和一个实数值数组 values 作为已知条件，其中 equations[i] = [Ai, Bi] 和
+* values[i] 共同表示等式 Ai / Bi = values[i] 。每个 Ai 或 Bi 是一个表示单个变量的字符串。
+*
+* 另有一些以数组 queries 表示的问题，其中 queries[j] = [Cj, Dj] 表示第 j 个问题，请你根据已知条件找出 Cj / Dj
+* = ? 的结果作为答案。
+*
+* 返回 所有问题的答案 。如果存在某个无法确定的答案，则用 -1.0 替代这个答案。如果问题中出现了给定的已知条件中没有出现的字符串，也需要用 -1.0
+* 替代这个答案。
+*
+* 注意：输入总是有效的。你可以假设除法运算中不会出现除数为 0 的情况，且不存在任何矛盾的结果。
+*
+* 注意：未在等式列表中出现的变量是未定义的，因此无法确定它们的答案。
+*
+*
+*
+* 示例 1：
+*
+*
+* 输入：equations = [["a","b"],["b","c"]], values = [2.0,3.0], queries =
+* [["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]
+* 输出：[6.00000,0.50000,-1.00000,1.00000,-1.00000]
+* 解释：
+* 条件：a / b = 2.0, b / c = 3.0
+* 问题：a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ?
+* 结果：[6.0, 0.5, -1.0, 1.0, -1.0 ]
+* 注意：x 是未定义的 => -1.0
+*
+* 示例 2：
+*
+*
+* 输入：equations = [["a","b"],["b","c"],["bc","cd"]], values = [1.5,2.5,5.0],
+* queries = [["a","c"],["c","b"],["bc","cd"],["cd","bc"]]
+* 输出：[3.75000,0.40000,5.00000,0.20000]
+*
+*
+* 示例 3：
+*
+*
+* 输入：equations = [["a","b"]], values = [0.5], queries =
+* [["a","b"],["b","a"],["a","c"],["x","y"]]
+* 输出：[0.50000,2.00000,-1.00000,-1.00000]
+*
+*
+*
+*
+* 提示：
+*
+*
+* 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 由小写英文字母与数字组成
+*
+*
+*/
+package jzoffer
+
+// @lc code=start
+func calcEquation1(equations [][]string, values []float64, queries [][]string) (res []float64) {
+	// 建图
+	graph := make(map[string]map[string]float64)
+	for i, v := range equations {
+		if _, ok := graph[v[0]]; !ok {
+			graph[v[0]] = map[string]float64{v[1]: values[i]}
+		} else {
+			graph[v[0]][v[1]] = values[i]
+		}
+
+		if _, ok := graph[v[1]]; !ok {
+			graph[v[1]] = map[string]float64{v[0]: 1 / values[i]}
+		} else {
+			graph[v[1]][v[0]] = 1 / values[i]
+		}
+	}
+	res = make([]float64, len(queries))
+	// dfs 找起点
+	for i, v := range queries {
+		// 起点,终点 必须都在图里才有解
+		nodes0, ok := graph[v[0]]
+		if !ok {
+			res[i] = -1.0
+			continue
+		}
+		if _, ok := graph[v[1]]; !ok {
+			res[i] = -1.0
+			continue
+		}
+		// 都在图里,且相同的 直接返回1
+		if v[0] == v[1] {
+			res[i] = 1.0
+			continue
+		}
+		// 在图里有对应的edge
+		if val, ok := nodes0[v[1]]; ok {
+			res[i] = val
+			continue
+		}
+
+		// bfs查找多层的路径,把边的权重带上
+		type edgeNode struct {
+			node   string
+			weight float64
+		}
+		queue := []edgeNode{}
+		for k := range nodes0 {
+			queue = append(queue, edgeNode{k, nodes0[k]})
+		}
+		visited := map[string]bool{v[0]: true}
+		for len(queue) > 0 {
+			top := queue[len(queue)-1]
+			queue = queue[:len(queue)-1]
+			if top.node == v[1] {
+				res[i] = top.weight
+				break
+			}
+			visited[top.node] = true
+			for k, kWeight := range graph[top.node] {
+				if visited[k] {
+					continue
+				}
+				queue = append(queue, edgeNode{k, kWeight * top.weight})
+			}
+		}
+		if res[i] < 0.0000000000000000000001 { // 没有设置过值的0 改成-1
+			res[i] = -1.0
+		}
+	}
+	return
+}
+
+func calcEquation(equations [][]string, values []float64, queries [][]string) (res []float64) {
+	// 建图
+	graph := make(map[string]map[string]float64)
+	for i, v := range equations {
+		if _, ok := graph[v[0]]; !ok {
+			graph[v[0]] = map[string]float64{v[1]: values[i]}
+		} else {
+			graph[v[0]][v[1]] = values[i]
+		}
+
+		if _, ok := graph[v[1]]; !ok {
+			graph[v[1]] = map[string]float64{v[0]: 1 / values[i]}
+		} else {
+			graph[v[1]][v[0]] = 1 / values[i]
+		}
+	}
+	res = make([]float64, len(queries))
+	// dfs 找起点
+	for i, v := range queries {
+		start, end := v[0], v[1]
+		nodes0, ok0 := graph[start]
+		_, ok1 := graph[end]
+		if !ok0 || !ok1 { // 起点,终点 必须都在图里才有解
+			res[i] = -1.0
+			continue
+		}
+		if start == end { // 都在图里,且相同的 直接返回1
+			res[i] = 1.0
+			continue
+		}
+
+		// bfs查找多层的路径,把边的权重带上
+		type edgeNode struct {
+			node   string
+			weight float64
+		}
+		queue := []edgeNode{}
+		for k := range nodes0 {
+			queue = append(queue, edgeNode{k, nodes0[k]})
+		}
+		visited := map[string]bool{start: true}
+		for len(queue) > 0 {
+			top := queue[len(queue)-1]
+			queue = queue[:len(queue)-1]
+			if top.node == end {
+				res[i] = top.weight
+				break
+			}
+			visited[top.node] = true
+			for k, kWeight := range graph[top.node] {
+				if visited[k] {
+					continue
+				}
+				queue = append(queue, edgeNode{k, kWeight * top.weight})
+			}
+		}
+		if res[i] < 0.0000000000000000000001 { // 没有设置过值的0 改成-1
+			res[i] = -1.0
+		}
+	}
+	return
+}
+
+// @lc code=end

go/bfs-dfs/399/399_test.go

@@ -0,0 +1,32 @@
+package jzoffer
+
+import (
+	"fmt"
+	"testing"
+)
+
+func Test399(t *testing.T) {
+	fmt.Println(calcEquation(
+		// [["a","b"],["c","b"],["d","b"],["w","x"],["y","x"],["z","x"],["w","d"]]
+		[][]string{
+			{"a", "b"}, {"c", "b"}, {"d", "b"}, {"w", "x"}, {"y", "x"}, {"z", "x"}, {"w", "d"}},
+		[]float64{2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0},
+		// [["a","c"],["b","c"],["a","e"],["a","a"],["x","x"],["a","z"]]
+		[][]string{{"a", "c"}, {"b", "c"}, {"a", "e"}, {"a", "a"}, {"x", "x"}, {"a", "z"}}))
+
+	/*
+	 * 输入：equations = [["a","b"],["b","c"]], values = [2.0,3.0], queries =
+	 * [["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]
+	 * 输出：[6.00000,0.50000,-1.00000,1.00000,-1.00000]
+	 * 解释：
+	 * 条件：a / b = 2.0, b / c = 3.0
+	 * 问题：a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ?
+	 * 结果：[6.0, 0.5, -1.0, 1.0, -1.0 ]
+	 * 注意：x 是未定义的 => -1.0
+	 */
+	fmt.Println(calcEquation(
+		[][]string{{"a", "b"}, {"b", "c"}},
+		[]float64{2.0, 3.0},
+		[][]string{{"a", "c"}, {"b", "a"}, {"a", "e"}, {"a", "a"}, {"x", "x"}}))
+
+}