Horje
Segment Tree for Range Addition and Range Minimum Query

Given an array of size N initially filled with 0s. There are Q queries to be performed, and each query can be one of two types:

  • Type 1 (1, L, R, X): Add X to all elements in the segment from L to R−1.
  • Type 2 (2, L, R): Find the minimum value in the segment from L to R−1.

Example:

Input: n = 5, q = 6, queries = {
{1, 0, 3, 3},
{2, 1, 2},
{1, 1, 4, 4},
{2, 1, 3},
{2, 1, 4},
{2, 3, 5} }
Output:
3
7
4
0

Approach:

The idea is to use Segment Tree with Lazy Propagation. It’s used to efficiently perform range update and range query operations on an array.

  • The build function constructs the segment tree from the input array.
  • The update function updates a range of values in the array and marks nodes for lazy updates.
  • The query function finds the minimum value in a range, taking into account any pending lazy updates.

Steps-by-step approach:

  • Define constants for the maximum size of the array and the segment tree.
  • Create a function to build the segment tree recursively.
  • Create a function to update a range in the array with lazy propagation.
  • Create a function to query a range in the array with lazy propagation.
  • In the main function:
    • Build the initial segment tree with zeros.
    • Define queries as a vector of vectors.
    • For each query:
      • If it’s a type 1 query, update the array using lazy propagation.
      • If it’s a type 2 query, query the array and print the result.

Below is the implementation of the above approach:

C++

#include<bits/stdc++.h>
using namespace std;
 
const int MAX = 1e5; // Max size of array
int tree[4*MAX]; // Segment tree
int lazy[4*MAX]; // Lazy array to propagate updates
 
// Function to build the tree
void build(int node, int start, int end)
{
    if(start == end)
    {
        // Leaf node will have a single element
        tree[node] = 0;
    }
    else
    {
        int mid = (start + end) / 2;
        // Recur for the 2 children
        build(2*node, start, mid);
        build(2*node+1, mid+1, end);
        // Internal node will have the minimum of both of its children
        tree[node] = min(tree[2*node], tree[2*node+1]);
    }
}
 
// Function to update a node
void update(int node, int start, int end, int l, int r, int val)
{
    if(lazy[node] != 0)
    {
        // This node needs to be updated
        tree[node] += lazy[node]; // Update it
        if(start != end)
        {
            lazy[node*2] += lazy[node]; // Mark child as lazy
            lazy[node*2+1] += lazy[node]; // Mark child as lazy
        }
        lazy[node] = 0; // Reset it
    }
    if(start > end or start > r or end < l) return; // Current segment is not within range [l, r]
    if(start >= l and end <= r)
    {
        // Segment is fully within range
        tree[node] += val;
        if(start != end)
        {
            // Not leaf node
            lazy[node*2] += val;
            lazy[node*2+1] += val;
        }
        return;
    }
    int mid = (start + end) / 2;
    update(node*2, start, mid, l, r, val); // Updating left child
    update(node*2 + 1, mid + 1, end, l, r, val); // Updating right child
    tree[node] = min(tree[node*2], tree[node*2+1]); // Updating root with min value
}
 
// Function to query the tree
int query(int node, int start, int end, int l, int r)
{
    if(start > end or start > r or end < l) return MAX; // Out of range
    if(lazy[node] != 0)
    {
        // This node needs to be updated
        tree[node] += lazy[node]; // Update it
        if(start != end)
        {
            lazy[node*2] += lazy[node]; // Mark child as lazy
            lazy[node*2+1] += lazy[node]; // Mark child as lazy
        }
        lazy[node] = 0; // Reset it
    }
    if(start >= l and end <= r) // Current segment is totally within range [l, r]
        return tree[node];
    int mid = (start + end) / 2;
    int p1 = query(node*2, start, mid, l, r); // Query left child
    int p2 = query(node*2 + 1, mid + 1, end, l, r); // Query right child
    return min(p1, p2);
}
 
int main()
{
    int n = 5;
    build(1, 0, n-1);
 
    // Define the queries
    vector<vector<int>> queries = {
        {1, 0, 3, 3},
        {2, 1, 2},
        {1, 1, 4, 4},
        {2, 1, 3},
        {2, 1, 4},
        {2, 3, 5}
    };
 
    for(auto &q : queries)
    {
        int type = q[0];
        if(type == 1)
        {
            int l = q[1], r = q[2], x = q[3];
            update(1, 0, n-1, l, r-1, x); // Update the array
        }
        else if(type == 2)
        {
            int l = q[1], r = q[2];
            int ans = query(1, 0, n-1, l, r-1); // Query the array
            cout << ans << endl;
        }
    }
    return 0;
}

Java

import java.util.*;
 
public class SegmentTree {
    static final int MAX = 100000; // Max size of array
    static int[] tree = new int[4 * MAX]; // Segment tree
    static int[] lazy = new int[4 * MAX]; // Lazy array to propagate updates
 
    // Function to build the tree
    static void build(int node, int start, int end) {
        if (start == end) {
            // Leaf node will have a single element
            tree[node] = 0;
        } else {
            int mid = (start + end) / 2;
            // Recur for the 2 children
            build(2 * node, start, mid);
            build(2 * node + 1, mid + 1, end);
            // Internal node will have the minimum of both of its children
            tree[node] = Math.min(tree[2 * node], tree[2 * node + 1]);
        }
    }
 
    // Function to update a node
    static void update(int node, int start, int end, int l, int r, int val) {
        if (lazy[node] != 0) {
            // This node needs to be updated
            tree[node] += lazy[node]; // Update it
            if (start != end) {
                lazy[node * 2] += lazy[node]; // Mark left child as lazy
                lazy[node * 2 + 1] += lazy[node]; // Mark right child as lazy
            }
            lazy[node] = 0; // Reset it
        }
        if (start > end || start > r || end < l)
            return; // Current segment is not within range [l, r]
        if (start >= l && end <= r) {
            // Segment is fully within range
            tree[node] += val;
            if (start != end) {
                // Not leaf node
                lazy[node * 2] += val;
                lazy[node * 2 + 1] += val;
            }
            return;
        }
        int mid = (start + end) / 2;
        update(node * 2, start, mid, l, r, val); // Updating left child
        update(node * 2 + 1, mid + 1, end, l, r, val); // Updating right child
        tree[node] = Math.min(tree[node * 2], tree[node * 2 + 1]); // Updating root with min value
    }
 
    // Function to query the tree
    static int query(int node, int start, int end, int l, int r) {
        if (start > end || start > r || end < l)
            return MAX; // Out of range
        if (lazy[node] != 0) {
            // This node needs to be updated
            tree[node] += lazy[node]; // Update it
            if (start != end) {
                lazy[node * 2] += lazy[node]; // Mark left child as lazy
                lazy[node * 2 + 1] += lazy[node]; // Mark right child as lazy
            }
            lazy[node] = 0; // Reset it
        }
        if (start >= l && end <= r)
            return tree[node]; // Current segment is totally within range [l, r]
        int mid = (start + end) / 2;
        int p1 = query(node * 2, start, mid, l, r); // Query left child
        int p2 = query(node * 2 + 1, mid + 1, end, l, r); // Query right child
        return Math.min(p1, p2);
    }
 
    public static void main(String[] args) {
        int n = 5;
        build(1, 0, n - 1);
 
        // Define the queries
        List<int[]> queries = Arrays.asList(
            new int[]{1, 0, 3, 3},
            new int[]{2, 1, 2},
            new int[]{1, 1, 4, 4},
            new int[]{2, 1, 3},
            new int[]{2, 1, 4},
            new int[]{2, 3, 5}
        );
 
        for (int[] q : queries) {
            int type = q[0];
            if (type == 1) {
                int l = q[1], r = q[2], x = q[3];
                update(1, 0, n - 1, l, r - 1, x); // Update the array
            } else if (type == 2) {
                int l = q[1], r = q[2];
                int ans = query(1, 0, n - 1, l, r - 1); // Query the array
                System.out.println(ans);
            }
        }
    }
}

C#

using System;
using System.Collections.Generic;
 
class SegmentTree
{
    const int MAX = 100000; // Max size of array
    int[] tree = new int[4 * MAX]; // Segment tree
    int[] lazy = new int[4 * MAX]; // Lazy array to propagate updates
 
    // Function to build the tree
    void Build(int node, int start, int end)
    {
        if (start == end)
        {
            // Leaf node will have a single element
            tree[node] = 0;
        }
        else
        {
            int mid = (start + end) / 2;
            // Recur for the 2 children
            Build(2 * node, start, mid);
            Build(2 * node + 1, mid + 1, end);
            // Internal node will have the minimum of both of its children
            tree[node] = Math.Min(tree[2 * node], tree[2 * node + 1]);
        }
    }
 
    // Function to update a node
    void Update(int node, int start, int end, int l, int r, int val)
    {
        if (lazy[node] != 0)
        {
            // This node needs to be updated
            tree[node] += lazy[node]; // Update it
            if (start != end)
            {
                lazy[node * 2] += lazy[node]; // Mark child as lazy
                lazy[node * 2 + 1] += lazy[node]; // Mark child as lazy
            }
            lazy[node] = 0; // Reset it
        }
        if (start > end || start > r || end < l) return; // Current segment is not within range [l, r]
        if (start >= l && end <= r)
        {
            // Segment is fully within range
            tree[node] += val;
            if (start != end)
            {
                // Not a leaf node
                lazy[node * 2] += val;
                lazy[node * 2 + 1] += val;
            }
            return;
        }
        int mid = (start + end) / 2;
        Update(node * 2, start, mid, l, r, val); // Updating left child
        Update(node * 2 + 1, mid + 1, end, l, r, val); // Updating right child
        tree[node] = Math.Min(tree[node * 2], tree[node * 2 + 1]); // Updating root with min value
    }
 
    // Function to query the tree
    int Query(int node, int start, int end, int l, int r)
    {
        if (start > end || start > r || end < l) return int.MaxValue; // Out of range
        if (lazy[node] != 0)
        {
            // This node needs to be updated
            tree[node] += lazy[node]; // Update it
            if (start != end)
            {
                lazy[node * 2] += lazy[node]; // Mark child as lazy
                lazy[node * 2 + 1] += lazy[node]; // Mark child as lazy
            }
            lazy[node] = 0; // Reset it
        }
        if (start >= l && end <= r) // Current segment is totally within range [l, r]
            return tree[node];
        int mid = (start + end) / 2;
        int p1 = Query(node * 2, start, mid, l, r); // Query left child
        int p2 = Query(node * 2 + 1, mid + 1, end, l, r); // Query right child
        return Math.Min(p1, p2);
    }
 
    static void Main()
    {
        int n = 5;
        var segmentTree = new SegmentTree();
        segmentTree.Build(1, 0, n - 1);
 
        // Define the queries
        var queries = new List<int[]>()
        {
            new int[] {1, 0, 3, 3},
            new int[] {2, 1, 2},
            new int[] {1, 1, 4, 4},
            new int[] {2, 1, 3},
            new int[] {2, 1, 4},
            new int[] {2, 3, 5}
        };
 
        foreach (var q in queries)
        {
            int type = q[0];
            if (type == 1)
            {
                int l = q[1], r = q[2], x = q[3];
                segmentTree.Update(1, 0, n - 1, l, r - 1, x); // Update the array
            }
            else if (type == 2)
            {
                int l = q[1], r = q[2];
                int ans = segmentTree.Query(1, 0, n - 1, l, r - 1); // Query the array
                Console.WriteLine(ans);
            }
        }
    }
}

Javascript

const MAX = 1e5; // Max size of array
let tree = new Array(4*MAX).fill(0); // Segment tree
let lazy = new Array(4*MAX).fill(0); // Lazy array to propagate updates
 
// Function to build the tree
function build(node, start, end) {
    if(start === end) {
        // Leaf node will have a single element
        tree[node] = 0;
    } else {
        let mid = Math.floor((start + end) / 2);
        // Recur for the 2 children
        build(2*node, start, mid);
        build(2*node+1, mid+1, end);
        // Internal node will have the minimum of both of its children
        tree[node] = Math.min(tree[2*node], tree[2*node+1]);
    }
}
 
// Function to update a node
function update(node, start, end, l, r, val) {
    if(lazy[node] !== 0) {
        // This node needs to be updated
        tree[node] += lazy[node]; // Update it
        if(start !== end) {
            lazy[node*2] += lazy[node]; // Mark child as lazy
            lazy[node*2+1] += lazy[node]; // Mark child as lazy
        }
        lazy[node] = 0; // Reset it
    }
    if(start > end || start > r || end < l) return; // Current segment is not within range [l, r]
    if(start >= l && end <= r) {
        // Segment is fully within range
        tree[node] += val;
        if(start !== end) {
            // Not leaf node
            lazy[node*2] += val;
            lazy[node*2+1] += val;
        }
        return;
    }
    let mid = Math.floor((start + end) / 2);
    update(node*2, start, mid, l, r, val); // Updating left child
    update(node*2 + 1, mid + 1, end, l, r, val); // Updating right child
    tree[node] = Math.min(tree[node*2], tree[node*2+1]); // Updating root with min value
}
 
// Function to query the tree
function query(node, start, end, l, r) {
    if(start > end || start > r || end < l) return MAX; // Out of range
    if(lazy[node] !== 0) {
        // This node needs to be updated
        tree[node] += lazy[node]; // Update it
        if(start !== end) {
            lazy[node*2] += lazy[node]; // Mark child as lazy
            lazy[node*2+1] += lazy[node]; // Mark child as lazy
        }
        lazy[node] = 0; // Reset it
    }
    if(start >= l && end <= r) // Current segment is totally within range [l, r]
        return tree[node];
    let mid = Math.floor((start + end) / 2);
    let p1 = query(node*2, start, mid, l, r); // Query left child
    let p2 = query(node*2 + 1, mid + 1, end, l, r); // Query right child
    return Math.min(p1, p2);
}
 
// Main function
function main() {
    let n = 5;
    build(1, 0, n-1);
 
    // Define the queries
    let queries = [
        [1, 0, 3, 3],
        [2, 1, 2],
        [1, 1, 4, 4],
        [2, 1, 3],
        [2, 1, 4],
        [2, 3, 5]
    ];
 
    for(let q of queries) {
        let type = q[0];
        if(type === 1) {
            let l = q[1], r = q[2], x = q[3];
            update(1, 0, n-1, l, r-1, x); // Update the array
        } else if(type === 2) {
            let l = q[1], r = q[2];
            let ans = query(1, 0, n-1, l, r-1); // Query the array
            console.log(ans);
        }
    }
}
 
main();

Python3

MAX = int(1e5)  # Max size of array
tree = [0] * (4 * MAX)  # Segment tree
lazy = [0] * (4 * MAX)  # Lazy array to propagate updates
 
# Function to build the tree
def build(node, start, end):
    if start == end:
        # Leaf node will have a single element
        tree[node] = 0
    else:
        mid = (start + end) // 2
        # Recur for the 2 children
        build(2 * node, start, mid)
        build(2 * node + 1, mid + 1, end)
        # Internal node will have the minimum of both of its children
        tree[node] = min(tree[2 * node], tree[2 * node + 1])
 
# Function to update a node
def update(node, start, end, l, r, val):
    if lazy[node] != 0:
        # This node needs to be updated
        tree[node] += lazy[node]  # Update it
        if start != end:
            lazy[node * 2] += lazy[node]  # Mark child as lazy
            lazy[node * 2 + 1] += lazy[node]  # Mark child as lazy
        lazy[node] = 0  # Reset it
    if start > end or start > r or end < l:
        return  # Current segment is not within range [l, r]
    if start >= l and end <= r:
        # Segment is fully within range
        tree[node] += val
        if start != end:
            # Not leaf node
            lazy[node * 2] += val
            lazy[node * 2 + 1] += val
        return
    mid = (start + end) // 2
    update(node * 2, start, mid, l, r, val)  # Updating left child
    update(node * 2 + 1, mid + 1, end, l, r, val)  # Updating right child
    tree[node] = min(tree[node * 2], tree[node * 2 + 1])  # Updating root with min value
 
# Function to query the tree
def query(node, start, end, l, r):
    if start > end or start > r or end < l:
        return MAX  # Out of range
    if lazy[node] != 0:
        # This node needs to be updated
        tree[node] += lazy[node]  # Update it
        if start != end:
            lazy[node * 2] += lazy[node]  # Mark child as lazy
            lazy[node * 2 + 1] += lazy[node]  # Mark child as lazy
        lazy[node] = 0  # Reset it
    if start >= l and end <= r:  # Current segment is totally within range [l, r]
        return tree[node]
    mid = (start + end) // 2
    p1 = query(node * 2, start, mid, l, r)  # Query left child
    p2 = query(node * 2 + 1, mid + 1, end, l, r)  # Query right child
    return min(p1, p2)
 
# Main function
def main():
    n = 5
    build(1, 0, n - 1)
 
    # Define the queries
    queries = [
        [1, 0, 3, 3],
        [2, 1, 2],
        [1, 1, 4, 4],
        [2, 1, 3],
        [2, 1, 4],
        [2, 3, 5]
    ]
 
    for q in queries:
        type = q[0]
        if type == 1:
            l, r, x = q[1], q[2], q[3]
            update(1, 0, n - 1, l, r - 1, x)  # Update the array
        elif type == 2:
            l, r = q[1], q[2]
            ans = query(1, 0, n - 1, l, r - 1)  # Query the array
            print(ans)
 
main()

Output

3
7
4
0

Time Complexity: O(log n) per query and update, O(n) for the construction of the segment tree.
Auxiliary Space : O(n) for the segment tree.


 


Reffered: https://www.geeksforgeeks.org

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Category:
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Sub Category:
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