Path with Maximum Probability

Java/1514-Path with Maximum Probability.java

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+/*
+ You are given an undirected weighted graph of n nodes (0-indexed), represented by an edge list where edges[i] = [a, b] is an undirected edge connecting the nodes a and b with a probability of success of traversing that edge succProb[i].
+
+Given two nodes start and end, find the path with the maximum probability of success to go from start to end and return its success probability.
+
+If there is no path from start to end, return 0. Your answer will be accepted if it differs from the correct answer by at most 1e-5.
+
+ */
+
+ class Solution {
+    public double maxProbability(int n, int[][] edges, double[] succProb, int start_node, int end_node) {
+        double[] maxProb = new double[n];
+        maxProb[start_node] = 1.0;
+        for (int i = 0; i < n - 1; i++) {
+            boolean updated = false;
+            for (int j = 0; j < edges.length; j++) {
+                int u = edges[j][0];
+                int v = edges[j][1];
+                double prob = succProb[j];
+
+                if (maxProb[u] * prob > maxProb[v]) {
+                    maxProb[v] = maxProb[u] * prob;
+                    updated = true;
+                }
+                if (maxProb[v] * prob > maxProb[u]) {
+                    maxProb[u] = maxProb[v] * prob;
+                    vs   updated = true;
+                }
+            }
+            if (!updated) break;
+        }
+        return maxProb[end_node];
+    }
+}
+
+/*
+
+Example 1:
+
+Input: n = 3, edges = [[0,1],[1,2],[0,2]], succProb = [0.5,0.5,0.2], start = 0, end = 2
+Output: 0.25000
+ */

Java/874-Walking Robot Simulation.java

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+
+//https://leetcode.com/problems/walking-robot-simulation/
+
+//874. Walking Robot Simulation
+
+
+class Solution {
+    public int robotSim(int[] commands, int[][] obstacles) {
+               // Directions: north, east, south, west
+        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
+        int x = 0, y = 0;  // Robot's starting position
+        int dir = 0;       // Start facing north
+        int maxDistSquared = 0;  // Maximum distance squared from the origin
+
+        // Store obstacles as a set of strings "x,y"
+        Set<String> obstacleSet = new HashSet<>();
+        for (int[] obstacle : obstacles) {
+            obstacleSet.add(obstacle[0] + "," + obstacle[1]);
+        }
+
+        // Process each command
+        for (int command : commands) {
+            if (command == -2) {  // Turn left
+                dir = (dir + 3) % 4;  // Equivalent to turning left 90 degrees
+            } else if (command == -1) {  // Turn right
+                dir = (dir + 1) % 4;  // Equivalent to turning right 90 degrees
+            } else {  // Move forward
+                for (int i = 0; i < command; i++) {
+                    int nextX = x + directions[dir][0];
+                    int nextY = y + directions[dir][1];
+                    // Check if the next position is an obstacle
+                    if (!obstacleSet.contains(nextX + "," + nextY)) {
+                        x = nextX;
+                        y = nextY;
+                        // Update the maximum distance squared
+                        maxDistSquared = Math.max(maxDistSquared, x * x + y * y);
+                    } else {
+                        // Stop moving if there's an obstacle
+                        break;
+                    }
+                }
+            }
+        }
+
+        return maxDistSquared;
+    }
+}
+
+/*
+Example 1:
+
+Input: commands = [4,-1,3], obstacles = []
+
+Output: 25
+
+Explanation:
+
+The robot starts at (0, 0):
+
+Move north 4 units to (0, 4).
+Turn right.
+Move east 3 units to (3, 4).
+The furthest point the robot ever gets from the origin is (3, 4), which squared is 32 + 42 = 25 units away.
+ */