【題解】AtCoder ABC 177F – I hate Shortest Path Problem

#include <iostream>
using namespace std;

int h, w, st[200005 << 2], lazy[200005 << 2], inf = 0x3F3F3F3F;

void push(int x, int l, int mid){
    if (!lazy[x]) return;
    st[x<<1] = lazy[x];
    lazy[x<<1] = lazy[x];
    st[x<<1|1] = lazy[x]+(mid-l+1);
    lazy[x<<1|1] = lazy[x]+(mid-l+1);
    lazy[x] = 0;
}
void update(int x, int l, int r, int ul, int ur, int u){
    if (ul <= l && r <= ur){
        st[x] = u;
        lazy[x] = u;
        return;
    }
    int mid = (l+r) >> 1;
    push(x, l, mid);
    int del = 0;
    if (ul <= mid){
        update(x<<1, l, mid, ul, ur, u);
        del = mid-max(ul, l)+1;
    }
    if (mid < ur) update(x<<1|1, mid+1, r, ul, ur, u + del);
    st[x] = min(st[x<<1], st[x<<1|1]);
}
int query(int x, int l, int r, int q){
    if (q == 0) return inf;
    if (l == r) return st[x];
    int mid = (l+r) >> 1;
    push(x, l, mid);
    if (q <= mid) return query(x<<1, l, mid, q);
    else return query(x<<1|1, mid+1, r, q);
}

int main() {
    cin >> h >> w;
    for (int i = 1, a, b; i <= h; i++){
        cin >> a >> b;
        update(1, 1, w, a, b, query(1, 1, w, a-1)+1);
        if (st[1] > w) cout << -1 << "\n";
        else cout << st[1]+i << "\n";
    }
}