线段树
1 #include <iostream> 2 #define MAX_LEN 1000 3 using namespace std; 4 5 //arr代表需要查询的数组，tree代表根据查询数组建立的堆， start代表起始点， end代表终止点 6 void build_tree(int arr[], int tree[], int node, int start, int end){ 7 if(start == end){//探测到叶子节点，把数据存入叶子节点，然后返回 8 tree[node] = arr[start]; 9 }else{ 10 int mid = (start + end) / 2; 11 int left_node = 2 * node + 1;//左子节点 12 int right_node = 2 * node + 2;//右子节点 13 build_tree(arr, tree, left_node, start, mid); 14 build_tree(arr, tree, right_node, mid + 1, end); 15 tree[node] = tree[left_node] + tree[right_node]; //返回后将子节点的和更新到父节点 16 } 17 } 18 //idx为待更新值的下标val是更新后的值 19 void update_tree(int arr[], int tree[], int node, int start, int end, int idx, int val){ 20 if(start == end){//到达叶节点 21 arr[idx] = val;//将叶节点值更新 22 tree[node] = val; 23 }else{ 24 int mid = (start + end) / 2; 25 int left_node = node * 2 + 1; 26 int right_node = node * 2 + 2; 27 if(idx >= start && idx <= mid){ 28 update_tree(arr, tree, left_node, start, mid, idx, val); 29 }else{ 30 update_tree(arr, tree, right_node, mid + 1, end, idx, val); 31 } 32 tree[node] = tree[left_node] + tree[right_node];//将父节点更新 33 } 34 } 35 int query_tree(int arr[], int tree[], int node, int start, int end, int L, int R){ 36 if(R < start || L > end){//不是连续区间 37 return 0; 38 }else if(L <= start && end <= R){//树上存在区间在查询的区间范围内 39 return tree[node];//将该区间的和返回 40 }else if(start == end){//查到叶子节点 41 return tree[node]; 42 }else{//查询区间在树的俩个不同的区段中 43 int mid = (start + end) / 2; 44 int left_node = 2 * node + 1; 45 int right_node = 2 * node + 2; 46 int sum_left = query_tree(arr, tree, left_node, start, mid, L, R); 47 int sum_right = query_tree(arr, tree, right_node, mid + 1, end, L, R); 48 return sum_left + sum_right;//返回该区段和 49 } 50 } 51 int main(){ 52 int arr[] = {1,3,5,7,9,11}; 53 int size = 6; 54 int tree[MAX_LEN] = {0}; 55 build_tree(arr, tree, 0, 0, size - 1);//将上述序列存入线段树 56 int i; 57 for(i = 0; i < 15; i++){ 58 printf("tree[%d] = %d\n", i, tree[i]); 59 } 60 printf("\n"); 61 update_tree(arr, tree, 0, 0, size - 1, 4, 6);//将下标为4的位置更新，还需要更新整个树 62 for(i = 0; i < 15; i++){ 63 printf("tree[%d] = %d\n", i, tree[i]); 64 } 65 int s = query_tree(arr, tree, 0, 0, size - 1,2, 5);//查询所求和 66 cout << s; 67 return 0; 68 }
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