https://leetcode.cn/problems/three-equal-parts/

Author: masx200

README.md

@@ -10,6 +10,8 @@ leetcode 测试
 
 ##### 包含的内容如下
 
+https://leetcode.cn/problems/three-equal-parts/
+
 https://leetcode.cn/problems/number-of-pairs-satisfying-inequality/
 
 https://leetcode.cn/problems/count-of-smaller-numbers-after-self/

three-equal-parts/index.ts

@@ -0,0 +1,45 @@
+import sum from "https://esm.sh/[email protected]/sum?dts";
+
+export default function threeEqualParts(arr: number[]): number[] {
+    const summ = sum(arr);
+    if (summ % 3 !== 0) {
+        return [-1, -1];
+    }
+    if (summ === 0) {
+        return [0, 2];
+    }
+
+    const partial = Math.floor(summ / 3);
+    let first = 0,
+        second = 0,
+        third = 0,
+        cur = 0;
+    for (let i = 0; i < arr.length; i++) {
+        if (arr[i] === 1) {
+            if (cur === 0) {
+                first = i;
+            } else if (cur === partial) {
+                second = i;
+            } else if (cur === 2 * partial) {
+                third = i;
+            }
+            cur++;
+        }
+    }
+
+    const len = arr.length - third;
+    if (first + len <= second && second + len <= third) {
+        let i = 0;
+        while (third + i < arr.length) {
+            if (
+                arr[first + i] !== arr[second + i] ||
+                arr[first + i] !== arr[third + i]
+            ) {
+                return [-1, -1];
+            }
+            i++;
+        }
+        return [first + len - 1, second + len];
+    }
+    return [-1, -1];
+}

three-equal-parts/test.ts

@@ -0,0 +1,16 @@
+import { assertEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
+import threeEqualParts from "./index.ts";
+Deno.test("three-equal-parts", () => {
+    assertEquals(
+        [
+            [1, 0, 1, 0, 1],
+            [1, 1, 0, 1, 1],
+            [1, 1, 0, 0, 1],
+        ].map(threeEqualParts),
+        [
+            [0, 3],
+            [-1, -1],
+            [0, 2],
+        ],
+    );
+});