Add solution #934

Author: JoshCrozier

Diff for: README.md

@@ -743,6 +743,7 @@
 931|[Minimum Falling Path Sum](./solutions/0931-minimum-falling-path-sum.js)|Medium|
 932|[Beautiful Array](./solutions/0932-beautiful-array.js)|Medium|
 933|[Number of Recent Calls](./solutions/0933-number-of-recent-calls.js)|Easy|
+934|[Shortest Bridge](./solutions/0934-shortest-bridge.js)|Medium|
 937|[Reorder Data in Log Files](./solutions/0937-reorder-data-in-log-files.js)|Medium|
 966|[Vowel Spellchecker](./solutions/0966-vowel-spellchecker.js)|Medium|
 970|[Powerful Integers](./solutions/0970-powerful-integers.js)|Easy|

Diff for: solutions/0934-shortest-bridge.js

@@ -0,0 +1,62 @@
+/**
+ * 934. Shortest Bridge
+ * https://leetcode.com/problems/shortest-bridge/
+ * Difficulty: Medium
+ *
+ * You are given an n x n binary matrix grid where 1 represents land and 0 represents water.
+ *
+ * An island is a 4-directionally connected group of 1's not connected to any other 1's.
+ * There are exactly two islands in grid.
+ *
+ * You may change 0's to 1's to connect the two islands to form one island.
+ *
+ * Return the smallest number of 0's you must flip to connect the two islands.
+ */
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var shortestBridge = function(grid) {
+  const n = grid.length;
+  const queue = [];
+  const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
+
+  outer: for (let i = 0; i < n; i++) {
+    for (let j = 0; j < n; j++) {
+      if (grid[i][j] === 1) {
+        findFirstIsland(i, j);
+        break outer;
+      }
+    }
+  }
+
+  let distance = 0;
+  while (queue.length) {
+    const size = queue.length;
+    for (let i = 0; i < size; i++) {
+      const [row, col] = queue.shift();
+      for (const [dx, dy] of directions) {
+        const newRow = row + dx;
+        const newCol = col + dy;
+        if (newRow < 0 || newRow >= n || newCol < 0 || newCol >= n
+            || grid[newRow][newCol] === 2) continue;
+        if (grid[newRow][newCol] === 1) return distance;
+        grid[newRow][newCol] = 2;
+        queue.push([newRow, newCol]);
+      }
+    }
+    distance++;
+  }
+
+  return distance;
+
+  function findFirstIsland(row, col) {
+    if (row < 0 || row >= n || col < 0 || col >= n || grid[row][col] !== 1) return;
+    grid[row][col] = 2;
+    queue.push([row, col]);
+    for (const [dx, dy] of directions) {
+      findFirstIsland(row + dx, col + dy);
+    }
+  }
+};