CF992E Nastya and King-Shamans 线段树

 

Code:

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 200000 + 5;
int n,q;
struct Segment_Tree
{
    # define lson (o << 1)
    # define rson (o << 1) | 1
    long long sumv[maxn << 2], maxv[maxn << 2];
    inline void maintain(int o){ 
        sumv[o] = sumv[lson] + sumv[rson];  
        maxv[o] = max(maxv[lson], maxv[rson]);  
    }
    void update(int l,int r,int pos, long long val, int o) {
        if(l > r || l > pos || r < pos) return ;
        if(l == r) { maxv[o] = sumv[o] = val;  return ; }
        int mid = (l + r) >> 1;
        update(l, mid, pos, val, lson);
        update(mid + 1, r, pos, val, rson);
        maintain(o); 
    }
    inline long long query(int l,int r,int L,int R,int o)
    {
        if(l > r || l > R || r < L) return 0;
        if(l >= L && r <= R) return sumv[o]; 
        int mid = (l + r) >> 1;
        return query(l, mid, L, R, lson) + query(mid + 1, r, L, R, rson);
    }
    inline int dfs(int l,int r,long long val, int o)
    {
        if(l == r) return l;
        int mid = (l + r) >> 1;
        if(maxv[lson] >= val) return dfs(l, mid, val, lson);
        else return dfs(mid + 1, r, val, rson);
    }
    int get(int l,int r, int L, int R, long long val,int o)
    {
        if(l > r || l > R || r < L) return -1; 
        if(l >= L && r <= R)
        {
            if(maxv[o] < val) return -1;
            return dfs(l, r, val, o);
        }
        int mid = (l + r) >> 1, h;
        h = get(l, mid, L, R, val, lson); if(h != -1) return h;
        h = get(mid + 1, r, L, R, val, rson); if(h != -1) return h;
        return -1;
    }
}T;
inline void solve()
{
    int l = 1;
    for(;;) {
        long long sumv = T.query(1, n, 1, l - 1, 1);           
        int pos = T.get(1, n, l, n, sumv, 1);
        if(pos == -1) { printf("-1\n"); return ; }
        else{
            if(sumv + T.query(1, n, l, pos - 1, 1) == T.query(1, n, pos, pos, 1)) { printf("%d\n", pos); return ;}
            l = pos + 1;
            if(l > n) { printf("-1\n"); return ;} 
        }
    } 
}
int main()
{
 
    scanf("%d%d",&n,&q);
    for(int i = 1;i <= n; ++i) { long long a; scanf("%I64d",&a); T.update(1, n, i, a, 1); }
    while(q--){
        int pos; 
        long long h; 
        scanf("%d%I64d",&pos, &h);
        T.update(1, n, pos, h, 1);
        solve();
    }
    return 0;
}