FINALLY

d12/main.ts

@@ -1,3 +1,4 @@
+import { assert } from 'console';
 import { env } from 'process';
 import * as rl from 'readline';
 
@@ -8,12 +9,15 @@ const term = rl.createInterface({
 
 function debug(obj: any) {
     if (env.DEBUG || env.TRACE)
-        console.log(obj);
+        console.log("\t".repeat(indentLevel) + obj);
 }
 
 function checkFit(field: string, len: number, idx: number) {
+    if (idx + len > field.length)
+        return false;
+
     for (let i = idx; i < idx + len; ++i) {
-        if (i >= field.length || field[i] == '.')
+        if (field[i] == '.')
             return false;
     }
 
@@ -26,19 +30,44 @@ function checkFit(field: string, len: number, idx: number) {
     return true;
 }
 
+function checkCovered(field: string, nums: number[], stack: number[]) {
+    assert(stack.length == nums.length);
+    for (let i = 0; i < field.length; ++i) {
+        if (field[i] == '#') {
+            let found = false;
+            for (let j = 0; j < stack.length; ++j) {
+                if (stack[j] <= i && i < stack[j] + nums[j]) {
+                    found = true;
+                    break;
+                }
+            }
+
+            if (!found) {
+                debug("rejecting " + stack);
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
+
 let indentLevel = 0;
-function recurse(nums: number[], field: string, idx: number) {
-    if (nums.length == 0) {
-        return 1;
+function recurse(nums: number[], numIdx: number, field: string, idx: number, stack: number[]) {
+    if (nums.length == numIdx) {
+        debug("checking final.");
+        return checkCovered(field, nums, stack) ? 1 : 0;
     }
 
     let count = 0;
     for (let i = idx; i < field.length; ++i) {
-        if (checkFit(field, nums[0], i)) {
+        if (checkFit(field, nums[numIdx], i)) {
             indentLevel++;
-            let sub = recurse(nums.slice(1), field, i + nums[0] + 1);
+            stack.push(i);
+            let sub = recurse(nums, numIdx + 1, field, i + nums[numIdx] + 1, stack);
+            stack.pop();
             indentLevel--;
-            debug("\t".repeat(indentLevel) + `counting ${sub} at ${i} with len = ${nums[0]}`);
+            debug(`counting ${sub} at ${i} with len = ${nums[numIdx]}`);
             count += sub;
         }
     }
@@ -51,14 +80,16 @@ function doTheThing(lines: string[]) {
     for (const line of lines) {
         const split = line.trim().split(" ").filter(i => i);
         const nums = split[1].split(",").map(x => Number(x));
-        const springs = split[0];
-        let res = recurse(nums, springs, 0);
-        console.log(`${springs} ${res}`);
+        let springs = split[0];
+        let stack: number[] = [];
+        // springs = ".............................................................." +  springs + "...................................................................";
+        let res = recurse(nums, 0, springs, 0, stack);
+        console.log(`${line} ${res}`);
         sum += res;
     }
     console.log(`sum: ${sum}`);
 }
 
 let lines: string[] = [];
-term.on("line", (input: string) => { lines.push(input) });
+term.on("line", (input: string) => { lines.push(input); });
 term.on("close", () => doTheThing(lines));