最大数

此题是一道适合线段树初学者拿来练手的好题，不需要过多的复杂操作（如pushdown, lazy tag等）。

此题需要做的只是在末尾加点和区间查询最大值操作即可。

Code：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
//Mystery_Sky
//
#define M 1000005
#define maxn 1000010
#define ll long long
#define Mid (l+r)>>1
struct Tree{
    int x;
    Tree *lc, *rc;
}dizhi[M<<1], *root = &dizhi[0];

int m, d, t=0, T;

void build(Tree *tree, int l, int r)
{
    if(l == r) {
        tree->x = 0;
        return;
    }
    int mid = Mid;
    tree->lc = &dizhi[++t];
    tree->rc = &dizhi[++t];
    build(tree->lc, l, mid);
    build(tree->rc, mid+1, r);
    tree->x = max(tree->lc->x, tree->rc->x);
}

void update(Tree *tree, int l, int r, int x, int d)
{
    if(l == r) {
        tree->x = d;
        return;
    }
    int mid = Mid;
    if(x <= mid) update(tree->lc, l, mid, x, d);
    else update(tree->rc, mid+1, r, x, d);
    tree->x = max(tree->lc->x, tree->rc->x);    
}

int query(Tree *tree, int l, int r, int x, int y) 
{
    if(x <= l && y >= r) return tree->x;
    int mid = Mid;
    int ans = 0;
    if(x <= mid) ans = max(ans, query(tree->lc, l, mid, x, y));
    if(y > mid) ans = max(ans, query(tree->rc, mid+1, r, x, y));
    return ans;
}

int main() {
    scanf("%d%d", &m, &d);
    int n = 1000000;
    build(root, 1, n);
    char a;
    int b;
    int num = 0;
    for(int i = 1; i <= m; i++) {
        cin >> a >> b;
        if(a == 'A') {
            num++;
            update(root, 1, n, num, (b + T)%d);
        }
        if(a == 'Q') {
            T = query(root, 1, n, num-b+1, num);
            printf("%d\n", T);
        }
    }
    return 0;
}
扫码关注我们
微信号：SRE实战
拒绝背锅 运筹帷幄