39 lines
1001 B
Java
39 lines
1001 B
Java
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public class FenwickTree2D {
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public static void add(int[][] t, int r, int c, int value) {
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for (int i = r; i < t.length; i |= i + 1)
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for (int j = c; j < t[0].length; j |= j + 1)
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t[i][j] += value;
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}
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// sum[(0, 0), (r, c)]
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public static int sum(int[][] t, int r, int c) {
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int res = 0;
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for (int i = r; i >= 0; i = (i & (i + 1)) - 1)
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for (int j = c; j >= 0; j = (j & (j + 1)) - 1)
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res += t[i][j];
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return res;
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}
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// sum[(r1, c1), (r2, c2)]
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public static int sum(int[][] t, int r1, int c1, int r2, int c2) {
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return sum(t, r2, c2) - sum(t, r1 - 1, c2) - sum(t, r2, c1 - 1) + sum(t, r1 - 1, c1 - 1);
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}
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public static int get(int[][] t, int r, int c) {
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return sum(t, r, c, r, c);
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}
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public static void set(int[][] t, int r, int c, int value) {
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add(t, r, c, -get(t, r, c) + value);
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}
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// Usage example
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public static void main(String[] args) {
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int[][] t = new int[10][20];
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add(t, 0, 0, 1);
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add(t, 9, 19, -2);
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System.out.println(-1 == sum(t, 0, 0, 9, 19));
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}
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}
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