树状数组模板

单点更新区间查询

使用树状数组维护原数组即可

public class Test01 {static final int N = 10010;static int[] c = new int[N];static int n;public static void main(String[] args) {Scanner in = new Scanner(System.in);n = in.nextInt();for (int i = 1; i <= n; i++) {int x = in.nextInt();update(i, x);}// 这里执行单点修改的代码// q个查询，区间查询int q = in.nextInt();while (q-- > 0) {int l, r;l = in.nextInt();r = in.nextInt();System.out.println(sums(r) - sums(l - 1));}}/*** 更新原数组中的idx** @param idx* @param x*/public static void update(int idx, int x) {while (idx <= n) {c[idx] += x;idx += idx & -idx;}}/*** 求原数组中a[1...j]的和** @param j* @return*/public static int sums(int j) {int res = 0;while (j > 0) {res += c[j];j -= j & -j;}return res;}
}

区间更新单点查询

使用树状数组维护原数组的差分数组

/*** 树状数组* 区间修改 单点查询* 使用树状数组维护原数组的差分数组*/
public class Test02 {static final int N = 10010;static int[] c = new int[N];static int[] d = new int[N];static int n;public static void main(String[] args) {Scanner in = new Scanner(System.in);n = in.nextInt();for (int i = 1; i <= n; i++) {int x = in.nextInt();update(i, x);update(i + 1, -x);}// 这里执行区间修改的代码// 单点查询，输出原数组for(int i = 1; i <= n; i ++){System.out.print(getsum(i) + " ");}}/*** 如果对区间a[l...r]+x 即 update(l, x);update(r + 1, -x);* @param idx* @param x*/public static void update(int idx, int x) {while (idx <= n) {c[idx] += x;idx += idx & -idx;}}/*** 求原数组a[j]* @param j*/public static int getsum(int j) {int res = 0;while(j > 0){res += c[j];j -= j & -j;}return res;}
}