feat: 2258. Escape the Spreading Fire : BFS

Author: upupming

leetcode/残酷刷题/2258. Escape the Spreading Fire.js

@@ -0,0 +1,43 @@
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+const maximumMinutes = function (g) {
+  const m = g.length; const n = g[0].length
+  const fs = []
+  for (let i = 0; i < m; i++) {
+    for (let j = 0; j < n; j++) {
+      if (g[i][j] === 1) fs.push([i, j])
+    }
+  }
+  const p = bfs([[0, 0]]); const f = bfs(fs)
+  if (p[m - 1][n - 1] === 1e10) return -1
+  if (f[m - 1][n - 1] === 1e10) return 1e9
+  if (p[m - 1][n - 1] > f[m - 1][n - 1]) return -1
+  const D = f[m - 1][n - 1] - p[m - 1][n - 1]
+  if (getDirection(f) === 'both') return D - 1
+  if (getDirection(f) === getDirection(p)) return D - 1
+  return D
+
+  function getDirection (f) {
+    if (f[m - 2][n - 1] === f[m - 1][n - 2]) return 'both'
+    else if (f[m - 2][n - 1] < f[m - 1][n - 2]) return 'up'
+    return 'left'
+  }
+  function bfs (q) {
+    const d = Array(m).fill(0).map(() => Array(n).fill(1e10))
+    for (const [x, y] of q) d[x][y] = 0
+    while (q.length) {
+      const [x, y] = q.shift()
+      for (const [dx, dy] of [[0, 1], [0, -1], [-1, 0], [1, 0]]) {
+        const i = x + dx; const j = y + dy
+        if (i >= 0 && i < m && j >= 0 && j < n && g[i][j] !== 2) {
+          if (d[i][j] !== 1e10) continue
+          d[i][j] = Math.min(d[i][j], d[x][y] + 1)
+          q.push([i, j])
+        }
+      }
+    }
+    return d
+  }
+}

leetcode/残酷刷题/README.md

@@ -199,6 +199,7 @@
 - 2045. Second Minimum Time to Reach Destination
 - 1263. Minimum Moves to Move a Box to Their Target Location
     - Deque, 只有 0 和 1 两个边权
+- 2258. Escape the Spreading Fire
 
 #### 拓扑排序