68 lines
1.8 KiB
Java
68 lines
1.8 KiB
Java
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public class SegmentTreeIntervalAddMax {
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int n;
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int[] tmax;
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int[] tadd; // tadd[i] affects tmax[i], tadd[2*i+1] and tadd[2*i+2]
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void push(int root) {
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tmax[root] += tadd[root];
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tadd[2 * root + 1] += tadd[root];
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tadd[2 * root + 2] += tadd[root];
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tadd[root] = 0;
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}
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public SegmentTreeIntervalAddMax(int n) {
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this.n = n;
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tmax = new int[4 * n];
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tadd = new int[4 * n];
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}
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public int max(int from, int to) {
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return max(from, to, 0, 0, n - 1);
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}
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int max(int from, int to, int root, int left, int right) {
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if (from == left && to == right) {
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return tmax[root] + tadd[root];
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}
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push(root);
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int mid = (left + right) >> 1;
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int res = Integer.MIN_VALUE;
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if (from <= mid)
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res = Math.max(res, max(from, Math.min(to, mid), 2 * root + 1, left, mid));
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else if (to > mid)
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res = Math.max(res, max(Math.max(from, mid + 1), to, 2 * root + 2, mid + 1, right));
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return res;
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}
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public void add(int from, int to, int delta) {
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add(from, to, delta, 0, 0, n - 1);
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}
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void add(int from, int to, int delta, int root, int left, int right) {
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if (from == left && to == right) {
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tadd[root] += delta;
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return;
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}
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// push can be skipped for add, but is necessary for other operations such as set
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push(root);
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int mid = (left + right) >> 1;
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if (from <= mid)
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add(from, Math.min(to, mid), delta, 2 * root + 1, left, mid);
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if (to > mid)
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add(Math.max(from, mid + 1), to, delta, 2 * root + 2, mid + 1, right);
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tmax[root] = Math.max(tmax[2 * root + 1] + tadd[2 * root + 1], tmax[2 * root + 2] + tadd[2 * root + 2]);
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}
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// tests
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public static void main(String[] args) {
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SegmentTreeIntervalAddMax t = new SegmentTreeIntervalAddMax(10);
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t.add(0, 9, 1);
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t.add(2, 4, 2);
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t.add(3, 5, 3);
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System.out.println(t.max(0, 9));
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System.out.println(t.tmax[0] + t.tadd[0]);
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System.out.println(t.max(0, 0));
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}
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}
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