HDU 1166 - 敌兵布阵

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题目链接： 敌兵布阵

思路

区间修改和区间查询，用树状数组快速A了，可能是长时间不写线段树的原因，竟然忘了要开4倍数组，一直TLE。

  • 线段树
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#include <bits/stdc++.h>
using namespace std;
int seqtree[200001],n,p;
int a[200001];
int read()
{
    int x = 0, f = 1;
    char ch = getchar();
    while(ch < '0' || ch > '9')
    {
        if(ch == '-')
            f = -1;
        ch = getchar();
    }
    while(ch >= '0' && ch <= '9')
    {
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    return x * f;
}
void maketree(int node,int begin, int end)
{
    if(begin == end)
    {
        seqtree[node] = read();
        return;
    }
    int mid = (begin + end) >> 1;
    maketree(node << 1, begin, mid);
    maketree(node << 1|1, mid + 1,end);
    seqtree[node] = seqtree[node << 1] + seqtree[node << 1|1];
}
void update(int node,int begin,int end,int pos,int grade)
{
    if(pos < begin || pos > end)
        return ;
    if(begin == end && begin == pos)
    {
        seqtree[node] += grade;
        return ;
    }
    int mid = (begin + end) >> 1;
    update(node << 1,begin, mid, pos,grade);
    update(node << 1|1, mid + 1, end, pos, grade);
    seqtree[node] = seqtree[node << 1] + seqtree[node << 1|1];
}
int query(int node,int begin,int end,int l,int r)
{
    if(l > end || r < begin)
        return 0;
    else if(l <= begin &&  r >= end)
        return seqtree[node];
    int sum = 0;
    int mid = (begin + end) >> 1;
    sum += query(node << 1,begin,mid,l,r);
    sum += query(node << 1|1,mid + 1,end, l,r);
    return sum;
}
int main()
{
    int t,A,B,caser = 1;
    char s[101];
    scanf("%d",&t);
    while(t--)
    {
        printf("Case %d:\n",caser++);
        memset(seqtree,0,sizeof(seqtree));
        scanf("%d",&n);
        maketree(1,1,n);
        while(scanf("%s",s))
        {
            if(s[0] == 'E')
                break;
            else if(s[0] == 'Q')
            {
                scanf("%d %d",&A,&B);
                printf("%d\n",query(1,1,n,A,B));
            }
            else if(s[0] == 'A')
            {
                scanf("%d %d",&A,&B);
                update(1,1,n,A,B);
            }
            else if(s[0] == 'S')
            {
                scanf("%d %d",&A,&B);
                update(1,1,n,A,-B);
            }
        }
    }
}

  • 树状数组

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    #include <bits/stdc++.h>
    using namespace std;
    int tree[100001],n;
    int lowbit(int x)
    {
        return (x & (-x));
    }
    void update(int x,int k)
    {
        for(int i = x; i <= n; i += lowbit(i))
        {
            tree[i] += k;
        }
    }
    int Query(int x)
    {
        int sum = 0;
        for(int i = x; i > 0 ; i -= lowbit(i))
        {
            sum += tree[i];
        }
        return sum;
    }
    int main()
    {
        int t, num, A, B, caser = 1;
        string s;
        scanf("%d",&t);
        while(t--)
        {
            printf("Case %d:\n",caser++);
            memset(tree,0,sizeof(tree));
            scanf("%d",&n);
            for(int i = 1; i <= n ;++i)
            {
                scanf("%d",&num);
                update(i,num);
            }
            while(cin >> s)
            {
                if(s == "End")
                    break;
                if(s[0] == 'Q')
                {
                    scanf("%d %d",&A,&B);
                    cout << Query(B) - Query(A - 1) << endl;
                }
                else if(s[0] == 'A'){
                    scanf("%d %d",&A,&B);
                    update(A,B);
                }
                else{
                    scanf("%d %d",&A,&B);
                    update(A, -B);
                }
            }
        }
    }