DataStructureAndAlgorithm/2023206/main.cpp

#include <stdio.h>
#define TREE_SIZE 65536
#define NOTHING 65535
struct TreeNode {
    // int val;
    unsigned short size;
    unsigned short left;
    unsigned short right;
};

TreeNode tree[TREE_SIZE] = {0};
int vals[TREE_SIZE] = {0};
int tree_root = NOTHING;
int M, K, H;
long long total = 0;
int l = 0;

int insert_node(int num, int pos) {
    if (pos == NOTHING) {
        // The tree_root is -1!
        tree[l % K] = TreeNode{1, NOTHING, NOTHING};
        tree_root = l % K;
        vals[l % K] = num;
        return l % K;
    }
    tree[pos].size++;
    if (vals[pos] > num) {
        if (tree[pos].left == NOTHING) {
            tree[pos].left = l % K;
            tree[l % K] = TreeNode{1, NOTHING, NOTHING};
            vals[l % K] = num;
            return l % K;
        }
        else {
            return insert_node(num, tree[pos].left);
        }
    }
    else {
        if (tree[pos].right == NOTHING) {
            tree[pos].right = l % K;
            tree[l % K] = TreeNode{1, NOTHING, NOTHING};
            vals[l % K] = num;
            return l % K;
        }
        else {
            return insert_node(num, tree[pos].right);
        }
    }
}

int delete_node(int num, int pos) {
    if (pos == NOTHING) {
        return NOTHING;
    }

    if (vals[pos] < num) {
        tree[pos].size--;
        tree[pos].right = delete_node(num, tree[pos].right);
        return pos;
    }

    if (vals[pos] > num) {
        tree[pos].size--;
        tree[pos].left = delete_node(num, tree[pos].left);
        return pos;
    }

    // If reached here, tree[pos].val == num, so we are going to delete tree[pos]
    if (tree[pos].left == NOTHING) {
        // The case when left is null, right is something
        // and also the case when both left and right is null
        return tree[pos].right;
    }

    if (tree[pos].right == NOTHING) {
        // The case when left is something while right is null
        return tree[pos].left;
    }

    // Here, we deal with the case that both children exist.
    int parent = pos;
    int child = tree[parent].right;
    tree[parent].size--;
    while (tree[child].left < NOTHING) {
        parent = child;
        child = tree[child].left;
        tree[parent].size--;
    }

    if (parent == pos) {
        tree[parent].right = tree[child].right;
    }
    else {
        tree[parent].left = tree[child].right;
    }

    tree[child].left = tree[pos].left;
    tree[child].right = tree[pos].right;
    tree[child].size = tree[pos].size;
    return child;
}

int count_less_than(long long target, int pos) {
    if (pos == NOTHING) {
        return 0;
    }

    if (vals[pos] < target) {
        if (tree[pos].left == NOTHING) {
            return 1 + count_less_than(target, tree[pos].right);
        }
        return tree[tree[pos].left].size + 1 + count_less_than(target, tree[pos].right);
    }
    if (vals[pos] > target) {
        return count_less_than(target, tree[pos].left);
    }

    if (tree[pos].left == NOTHING) {
        return 1;
    }
    return 1 + tree[tree[pos].left].size;
}

int main() {
    scanf("%d %d %d", &M, &K, &H);
    int num = 0;

    for (l = 0; l < M; l++) {
        scanf("%d", &num);
        total += count_less_than(((long long)num) + H, tree_root) -
                 count_less_than(num - H - 1, tree_root);
        if (l >= K) {
            tree_root = delete_node(vals[l % K], tree_root);
        }
        insert_node(num, tree_root);
    }

    printf("%lld\n", total);
    return 0;
}