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src/main/java/com/dota/graph/Solution.java

@@ -67,4 +67,124 @@ class Solution {
 			}
 		}
 	}
+
+	int min = Integer.MAX_VALUE;
+
+	int N = 10001;
+	int[] union = new int[N];
+
+	int find(int x) {
+		while (union[x] != x) {
+			union[x] = union[union[x]];
+			x = union[x];
 		}
+		return x;
+	}
+
+	// 使用并查集
+	public int minimumEffortPath(int[][] heights) {
+		for (int i = 0; i < N; i++) {
+			union[i] = i;
+		}
+
+		int n = heights.length;
+		int m = heights[0].length;
+		List<int[]> list = new ArrayList<>(1000001);
+		for (int i = 0; i < n; i++) {
+			for (int j = 0; j < m; j++) {
+				int idx = index(i, j, n, m);
+				int i1 = index(i, j + 1, n, m);
+				int i2 = index(i + 1, j, n, m);
+				if (i1 != -1) {
+					int hei = Math.abs(heights[i][j]-heights[i][j+1]);
+					list.add(new int[]{idx, i1, hei});
+				}
+				if (i2 != -1) {
+					int hei = Math.abs(heights[i][j]-heights[i+1][j]);
+					list.add(new int[]{idx, i2, hei});
+				}
+			}
+		}
+
+		for (int[] ints : list) {
+			union[find(ints[0])] = find(ints[1]);
+			if (find(0)==find(n*m-1)) {
+				return ints[2];
+			}
+		}
+		return 0;
+	}
+
+	int index(int i, int j, int n, int m) {
+		if (i < 0 || j < 0 || i >= n || j >= m) {
+			return -1;
+		}
+
+		return (i * m) + j;
+	}
+}
+
+class Solution1 {
+
+	private int[] parent;
+	private Edge[] edges = new Edge[1000001];
+
+	public int minimumEffortPath(int[][] heights) {
+		int m = heights.length, n = heights[0].length;
+		if (m == 1 && n == 1) return 0;
+
+		parent = new int[m * n];
+		for (int i = 0; i < m * n; i++) parent[i] = i;
+
+		int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
+
+		for (int i = 0; i < m; i++) {
+			for (int j = 0; j < n; j++) {
+				if (i < m-1) {
+					int diff = Math.abs(heights[i][j] - heights[i+1][j]);
+					edges[diff] = new Edge(i * n + j, (i+1) * n + j, edges[diff]);
+					if(diff > max) max = diff;
+					if(diff < min) min = diff;
+				}
+
+				if (j < n-1) {
+					int diff = Math.abs(heights[i][j] - heights[i][j+1]);
+					edges[diff] = new Edge(i * n + j, i * n + (j+1), edges[diff]);
+					if(diff > max) max = diff;
+					if(diff < min) min = diff;
+				}
+			}
+		}
+
+		for(int i = min; i <= max; ++i){
+			for (Edge e = edges[i]; e != null; e = e.next) {
+				int xParent = find(e.x, parent), yParent = find(e.y, parent);
+				parent[xParent] = yParent;
+
+				if (find(0, parent) == find(m * n -1, parent)) return i;
+			}
+		}
+
+		return 0;
+	}
+
+	private int find(int x, int[] parent) {
+		while (parent[x] != x) {
+			parent[x] = parent[parent[x]];
+			x = parent[x];
+		}
+		return x;
+	}
+
+	class Edge {
+		int x, y;
+		Edge next;
+
+		Edge(int x, int y, Edge next) {
+			this.x = x;
+			this.y = y;
+			this.next = next;
+		}
+	}
+}
+