UVa 12299 RMQ with Shifts(线段树)

题目链接：http://acm.hust.edu.cn/vjudge/problem/23591

大意：给出n个数q个询问。对于query（a，b），输出区间（a，b）的数的最小值；对于shift（a0，a1，a2，......，an），则将第a1个数的值赋给a0，第a2个数赋给a1......，第an个数赋给an-1，第a0个数赋给an

思路：

线段树模板题，为了修改方便，可以先用一个额外的数组将这n个数保存下来。

#include<cstdio>
#include<cstring>
#include<iostream>
#include<cmath>
#include<vector>
#include<algorithm>
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define lc rt<<1
#define rc rt<<1|1
using namespace std;

typedef long long ll;
const int maxn = 100000 + 5;
const int INF = 1e9 + 10;
int min_[maxn<<2],arr[maxn];
int n,q;
int ql,qr;

vector<int> Query_(char *s)
{
    vector<int> ans;
    ans.clear();
    int len = strlen(s);
    int sum = 0;
    for (int i = 0; i < len; i++) {
        if (s[i] == ')' || s[i] == ',') {
            ans.push_back(sum);
            sum = 0;
        }
        else if (isdigit(s[i])) {
            sum *= 10;
            sum += s[i]-'0';
        }
    }
    return ans;
}

void build(int l, int r, int rt)
{
    if (l == r) min_[rt] = arr[l];
    else {
        int m = (l + r) >> 1;
        build(lson);
        build(rson);
        min_[rt] = min(min_[lc],min_[rc]);
    }
}

int query(int l, int r, int rt)
{
    if (ql <= l && r <= qr) return min_[rt];
    int m = (l + r) >> 1;
    int ans = INF;
    if (ql <= m) ans = min(ans, query(lson));
    if (m < qr) ans = min(ans,query(rson));
    return ans;
}

void update(int p, int x, int l, int r, int rt)
{
    if (l == r) min_[rt] = x;
    else {
        int m = (l + r) >> 1;
        if (p <= m) update(p,x,lson);
        else update(p,x,rson);
        min_[rt] = min(min_[lc], min_[rc]);
    }
}

int main()
{
    scanf("%d%d",&n,&q);
    for (int i = 1; i <= n; i++) scanf("%d",&arr[i]);
    build(1,n,1);
    while(q--) {
        char s[50];
        scanf("%s",s);
        vector<int> ha = Query_(s);
        if (s[0] == 'q') {
            ql = ha[0];
            qr = ha[1];
            printf("%d\n",query(1,n,1));
        }
        else{
            int t = arr[ha[0]];
            int len = ha.size() - 1;
            for (int i = 0; i < len; i++) {
                update(ha[i],arr[ha[i+1]],1,n,1);
                arr[ha[i]] = arr[ha[i+1]];
            }
            update(ha[len],t,1,n,1);
            arr[ha[len]] = t;
        }
    }
}