add segment tree with example 3479

segment-tree/3479 fruits-into-baskets-III.cpp

@@ -0,0 +1,63 @@
+/*  You are given two arrays of integers, fruits and baskets, each of length n, where fruits[i] represents the quantity of the ith type of fruit, and baskets[j] represents the capacity of the jth basket.
+
+    From left to right, place the fruits according to these rules:
+
+        1.Each fruit type must be placed in the leftmost available basket with a capacity greater than or equal to the quantity of that fruit type.
+        2.Each basket can hold only one type of fruit.
+        3.If a fruit type cannot be placed in any basket, it remains unplaced.
+
+    Return the number of fruit types that remain unplaced after all possible allocations are made.
+*/
+class SegmentTree {
+private:
+	vector<int> segVal;
+	void maintain(int node) {
+		segVal[node] = max(segVal[node * 2], segVal[node * 2 + 1]);
+	}
+	void build(const vector<int>& vec, int node, int left, int right) {
+		if (left == right) {
+			segVal[node] = vec[left];
+			return;
+		}
+		int mid = (left + right) / 2;
+		build(vec, node * 2, left, mid);
+		build(vec, node * 2 + 1, mid + 1, right);
+		maintain(node);
+	}
+public:
+	SegmentTree(const vector<int>& vec) {
+		size_t n = vec.size();
+		segVal.resize(2 << std::bit_width(n - 1));
+		build(vec, 1, 0, n - 1);
+	}
+	int findFirstAndUpdate(int node, int left, int right, int val) {
+		if (segVal[node] < val) {
+			return -1;	// not found;
+		}
+		if (left == right) {
+			segVal[node] = -1;	// update state
+			return left;
+		}
+		int mid = (left + right) / 2;
+		int idx = findFirstAndUpdate(node * 2, left, mid, val);
+		if (idx < 0) {
+			idx = findFirstAndUpdate(node * 2 + 1, mid + 1, right, val);
+		}
+		maintain(node);
+		return idx;
+	}
+};
+
+class Solution {
+public:
+    int numOfUnplacedFruits(vector<int>& fruits, vector<int>& baskets) {
+        SegmentTree t(baskets);
+        int n = baskets.size(), ans = 0;
+        for (int x : fruits) {
+            if (t.findFirstAndUpdate(1, 0, n - 1, x) < 0) {
+                ans++;
+            }
+        }
+        return ans;
+    }
+};