Update 1467-probability-of-a-two-boxes-having-the-same-number-of-distinct-balls.js

Author: everthis

1467-probability-of-a-two-boxes-having-the-same-number-of-distinct-balls.js

@@ -1,3 +1,71 @@
+/**
+ * @param {number[]} balls
+ * @return {number}
+ */
+const getProbability = function(balls) {
+  const k = balls.length;
+  const halfUsed = balls.reduce((acc, val) => acc + val, 0) / 2;
+  const startArray = new Array(k);
+  startArray.fill(0);
+  const perm = function (b1, b2) {
+    let p1, p2, s1, s2;
+    s1 = b1.reduce((acc, val) => acc + val, 0);
+    s2 = b2.reduce((acc, val) => acc + val, 0);
+    const fact = function (n) {
+      let f = 1;
+      for (let i = 2; i <= n; i++) f *= i;
+      return f;
+    };
+    p1 = fact(s1);
+    p2 = fact(s2);
+    b1.forEach((val) => {
+      if (val > 1) p1 /= fact(val);
+    });
+    b2.forEach((val) => {
+      if (val > 1) p2 /= fact(val);
+    });
+    return p1 * p2;
+  };
+
+  const getValidCombos = function (ballsUsed, colorNum = 0) {
+    let box1Used = ballsUsed.reduce((acc, val) => acc + val, 0);
+    let matches = { good: 0, total: 0 },
+      thisColorMax = halfUsed - box1Used;
+    if (colorNum === k - 1) {
+      if (thisColorMax > balls[colorNum]) return { good: 0, total: 0 };
+      ballsUsed[colorNum] = thisColorMax;
+      let ballsLeft = [];
+      let colorsUsed = [0, 0];
+      for (let i = 0; i < k; i++) {
+        ballsLeft[i] = balls[i] - ballsUsed[i];
+        if (ballsUsed[i] > 0) colorsUsed[0]++;
+        if (ballsLeft[i] > 0) colorsUsed[1]++;
+      }
+      let permutations = perm(ballsUsed, ballsLeft, k);
+      return {
+        good: colorsUsed[1] === colorsUsed[0] ? permutations : 0,
+        total: permutations,
+      };
+    }
+    thisColorMax = Math.min(thisColorMax, balls[colorNum]);
+    for (let i = 0; i <= thisColorMax; i++) {
+      let match = getValidCombos([...ballsUsed], colorNum + 1);
+      matches = {
+        good: matches.good + match.good,
+        total: matches.total + match.total,
+      };
+      ballsUsed[colorNum]++;
+    }
+    return matches;
+  };
+  let res = getValidCombos(startArray);
+  return res.good / res.total;
+};
+
+
+// another
+
+
 /**
  * @param {number[]} balls
  * @return {number}