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Author: MathProgrammer

C Programs/C Programs - 3/Light Switching.cpp

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+#include <cstdio>
+
+const int MAX_SIZE = 1e5, OFF = 0, ON = 1;
+int tree[3*MAX_SIZE];
+int lazy[3*MAX_SIZE] = {0};
+int light[MAX_SIZE] = {OFF};
+
+void build(int node, int start, int end)
+{
+    if(start == end)
+    {
+        tree[node] = light[start];
+        return;
+    }
+
+    int mid = (start + end)/2;
+    build(2*node, start, mid);
+    build(2*node + 1, mid + 1, end);
+
+    tree[node] = tree[2*node] + tree[2*node + 1];
+}
+
+void propagate(int node, int start, int end)
+{
+    int on_lights = tree[node];
+    int total_lights = end - (start - 1);
+    int off_lights = total_lights - on_lights;
+
+    if(lazy[node]%2 == 1)
+        tree[node] = off_lights;
+
+    if(start != end)
+    {
+        lazy[2*node] += lazy[node];
+        lazy[2*node + 1] += lazy[node];
+    }
+
+    lazy[node] = 0;
+}
+
+void update(int node, int start, int end, int query_start, int query_end)
+{
+    if(lazy[node] != 0)
+        propagate(node, start, end);
+
+    if(query_start > end || query_end < start)
+        return;
+
+    if(query_start <= start && end <= query_end)
+    {
+        int no_of_lights = end - (start - 1);
+        int no_of_on_lights = tree[node];
+        int no_of_off_lights = no_of_lights - no_of_on_lights;
+
+        tree[node] = no_of_off_lights;
+
+        if(start != end)
+        {
+            lazy[2*node]++;
+            lazy[2*node + 1]++;
+        }
+        return;
+    }
+
+    int mid = (start + end)/2;
+
+    update(2*node, start, mid, query_start, query_end);
+    update(2*node + 1, mid + 1, end, query_start, query_end);
+
+    tree[node] = tree[2*node] + tree[2*node + 1];
+}
+
+int query(int node, int start, int end, int query_start, int query_end)
+{
+    if(lazy[node] != 0)
+        propagate(node, start, end);
+
+    if(query_start > end || query_end < start)
+        return 0;
+
+    if(query_start <= start && end <= query_end)
+        return tree[node];
+
+    int mid = (start + end)/2;
+
+    int left_answer  = query(2*node, start, mid, query_start, query_end);
+    int right_answer = query(2*node + 1, mid + 1, end, query_start, query_end);
+
+    return (left_answer + right_answer);
+}
+
+int main()
+{
+    int no_of_lights, no_of_operations;
+    scanf("%d %d", &no_of_lights, &no_of_operations);
+
+    build(1, 1, no_of_lights);
+
+    while(no_of_operations--)
+    {
+        int type, left, right;
+        scanf("%d %d %d", &type, &left, &right);
+
+        if(type == 0)
+        {
+            update(1, 1, no_of_lights, left, right);
+        }
+        else if(type == 1)
+        {
+            int answer = query(1, 1, no_of_lights, left, right);
+            printf("%d\n", answer);
+        }
+    }
+    return 0;
+}