Merge pull request matthewsamuel95#269 from ThiagoWhispher/patch-2

Created Segment Tree and LCA

Author: matthewsamuel95

Data Structures/LCA/lca.cpp

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <vector>
+ using namespace std;
+ #define max 100
+#define lg_max 7
+ vector<int> graph[max];
+int parent[max][lg_max], level[max], lg[max];
+int n;
+ void log(){
+    for(int i=2; i<max; i++) lg[i] = lg[i/2] + 1;
+}
+ void dfs(int u, int p){
+    for(auto v: graph[u]){
+        if(v != p){
+            level[v] = level[u] + 1;
+            parent[v][0] = u;
+            dfs(v,u);
+        }
+    }
+}
+ void build(){
+    for(int j=1; j<=lg[n]; j++){
+        for(int i=1; i<=n; i++){
+            parent[i][j] = parent[parent[i][j-1]][j-1];
+        }
+    }
+}
+ int lca(int u, int v){
+    if(level[u] < level[v]) return lca(v, u);
+    for(int i=lg[n]; i>=0; i--){
+        if(level[u] - (1<<i) >= level[v]){
+            u = parent[u][i];
+        }
+    }
+    if(u == v) return u;
+    for(int i=lg[n]; i>=0; i--){
+        if(parent[u][i] != parent[v][i]){
+            u = parent[u][i];
+            v = parent[v][i];
+        }
+    }
+    return parent[u][0];
+}
+ int main(){
+    log();
+    int x, y;
+    scanf("%d", &n);
+    for(int i=0; i<n-1; i++){
+        scanf("%d%d", &x, &y);
+        graph[x].push_back(y);
+        graph[y].push_back(x);
+    }
+    dfs(1,1);
+    build();
+    scanf("%d%d", &x, &y);
+    printf("%d\n", lca(x, y));
+}

Data Structures/Segment Tree/segment_tree.cpp

@@ -0,0 +1,56 @@
+#include <stdio.h>
+
+using namespace std;
+
+#define MAX (int)10e6
+
+int values[MAX], tree[MAX * 4];
+
+int read(int id, int l, int r, int x, int y){
+    if(l > y || r < x) return 0;
+    else{
+        if(l >= x && r <= y) return tree[id];
+        else{
+            int mid = (l+r)/2;
+            int q1 = read(id*2, l, mid, x, y);
+            int q2 = read(id*2+1, mid+1, r, x, y);
+            return q1 + q2;
+        }
+    }
+}
+
+void update(int id, int l, int r, int p, int value){
+    if(l == r) tree[id] = value;
+    else{
+        int mid = (l+r)/2;
+        if(p <= mid) update(id*2, l, mid, p, value);
+        else update(id*2+1, mid+1, r, p, value);
+        tree[id] = tree[id*2] + tree[id*2+1];
+    }
+}
+
+void build(int id, int l, int r){
+    if(l == r) tree[id] = values[l];
+    else{
+        int mid = (l+r)/2;
+        build(id*2, l, mid);
+        build(id*2+1, mid+1, r);
+        tree[id] = tree[id*2] + tree[id*2+1];
+    }
+}
+
+int main(){
+    int n, q, x, y, opc;
+    scanf("%d %d", &n, &q);
+    for(int i=1; i<=n; i++) scanf("%d", &values[i]);
+    build(1, 1, n);
+    while(q--){
+        scanf("%d %d %d", &opc, &x, &y);
+        if(opc == 1){ //read
+            printf("%d\n", read(1, 1, n, x, y));
+        }else{ //update
+            update(1, 1, n, x, y);
+        }
+    }
+    return 0;
+}