线段树之单点更新

单点更新，其实就是对一个点进行更新。

HDU 1166

　　

#include <iostream>
#include <stdio.h>
#include <string.h>
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
const int MAX = 50010;
int tree[MAX<<2];
void Push(int rt){
    tree[rt] = tree[rt<<1]+tree[rt<<1|1];
}
void build(int l, int r, int rt){
    if(l == r){
        scanf("%d",&tree[rt]);
        return ;
    }
    int m = (l+r)>>1;
    build(lson);
    build(rson);
    Push(rt);
}
void update(int x, int p, int l, int r, int rt){
    if(l == r){
        tree[rt] += p;
        return;
    }
    int m = (l+r)>>1;
    if(m >=x)update(x,p,lson);
    else update(x,p,rson);
    Push(rt);
}
int query(int LL, int RR, int l, int r, int rt){
    if(LL <= l && r <= RR){
        return tree[rt];
    }
    int m = (l+r)>>1;
    int sum = 0;
    if(m >= LL) sum+=query(LL,RR,lson);
    if(m < RR) sum+=query(LL,RR,rson);
    return sum;
}
int main(){
    int t,n,k=1;
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        printf("Case %d:
",k++);
        build(1,n,1);
        char str[10];
        int l,r;
        while(scanf("%s",str)!=EOF){
            if(str[0] == 'E')break;
            scanf("%d %d",&l,&r);
            if(str[0] == 'Q'){
                printf("%d
",query(l,r,1,n,1));
            }else if(str[0] == 'A'){
                update(l,r,1,n,1);
            }else {
                update(l,-r,1,n,1);
            }
        }
    }
    return 0;
}

HDU - 2795

#include <iostream>
#include <cstdio>
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1

using namespace std;
const int maxn = 2e5+10;
int n, h, w;
int MAX[maxn<<2];
void PushUP(int rt){
    MAX[rt] = max(MAX[rt<<1], MAX[rt<<1|1]);
}

void build(int l, int r, int rt){//建立线段树
    MAX[rt] = w;
    if(l == r)return;
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
}
int query(int q, int l, int r, int rt){
    if(l == r){
        MAX[rt] -= q;//每次查询时减下q
        return l;
    }
    int m = (l + r) >> 1;
    int ret = (MAX[rt<<1] >= q)?query(q, lson):query(q, rson);//求出满足条件的最左边区间
    PushUP(rt);
    return ret;
}

int main()
{
    while(~scanf("%d%d%d",&h,&w,&n)){
        if(h > n) h = n;//这样建立的区间更少些
        build(1, h, 1);
        while(n--){
            int x;
            scanf("%d",&x);
            if(MAX[1] < x) printf("-1
");
            else printf("%d
",query(x, 1, h, 1));
        }
    }
    return 0;
}