HDU 1754 I Hate It（線段樹，區間最大值）

連結：

http://acm.hdu.edu.cn/showproblem.php?pid=1754

分析與總結：

線段樹求區間最大值，好像也沒什麼可講的。

代碼：

#include<iostream>#include<cstdio>#include<cstring>#define lson(x) (x<<1)#define rson(x) (lson(x)|1)using namespace std;typedef int Type;const int MAX_NODE = 200005<<2;struct node{    int left, right;    Type val;    int mid(){return (left+right)>>1;}    bool buttom(){return left==right;}};class SegTree{public:    void build(int cur,int left,int right){        t[cur].left  = left;        t[cur].right = right;        if(left == right){            scanf("%d",&t[cur].val);            return;        }        int m = t[cur].mid();        build(lson(cur),left,m);        build(rson(cur),m+1,right);        push_up(cur);    }    void update(int cur,int p,int data){        if(t[cur].buttom()){            t[cur].val = data;            return;        }        int m = t[cur].mid();        if(p <= m)            update(lson(cur),p,data);        else            update(rson(cur),p,data);        push_up(cur);    }    int query(int cur,int left,int right){        if(t[cur].left==left && t[cur].right==right){            return t[cur].val;        }        int m = t[cur].mid();        if(right <= m)            return query(lson(cur),left,right);        else if(left > m)            return query(rson(cur),left,right);        else            return max(query(lson(cur),left,m), query(rson(cur),m+1,right));    }private:    void push_up(int cur){        t[cur].val = max(t[lson(cur)].val,t[rson(cur)].val);    }private:    node t[MAX_NODE];};SegTree st;int main(){    int n,m,x,y;    char cmd[5];    while(~scanf("%d%d",&n,&m)){        st.build(1,1,n);        for(int i=0; i<m; ++i){            scanf("%s %d %d",cmd,&x,&y);            if(cmd[0] == 'Q') printf("%d\n", st.query(1,x,y));            else st.update(1,x,y);        }    }    return 0;}

 ——  生命的意義，在於賦予它意義士。

          原創 http://blog.csdn.net/shuangde800 ， By
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