fenwick.sublime-snippet

<snippet>
	<content><![CDATA[
struct fenwick {
    vector<int> fn;
    int n;
    void init(int _n) {
        n = _n;
        fn.resize(n+1, 0);
    }
    void add(int x, int val) {
        x++; // 1 based indexing
        while (x <= n) {
            fn[x] += val;
            x += (x & (-x));
        }
    }
    int query(int x) {
        // x++; // 1 based indexing
        int ans = 0;
        while (x) {
            ans += fn[x];
            x -= (x & (-x));
        }
        return ans;
    }
} bit;

// bit.init(n);
// for (i=0;i<n;i++) {
//     bit.add(i, a[i]);
// }
// cout<<bit.query(3);

]]></content>
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