HDU_1754_线段树

来源：互联网发布：数组的push和pop 编辑：程序博客网时间：2024/05/23 14:10

题意：区间最值问题，线段树模板水题：

#include <cstdio>#include <cstring>using namespace std;const int N = 200000 + 10;int maxnumb[N<<2];int MAX(int a, int b){    return a<b ? b : a;}void build(int l, int r, int rt){if(l == r){scanf("%d", &maxnumb[rt]);return ;}int m = (l+r) >> 1, rtt = rt << 1;build(l, m, rtt);build(m+1, r, rtt+1);maxnumb[rt] = MAX(maxnumb[rtt], maxnumb[rtt+1]);}void update(int p, int add, int l, int r, int rt){if(l == r){maxnumb[rt] = add;return ;}int m = (l+r) >> 1, rtt = rt << 1;if(p <= m)update(p, add, l, m, rtt);elseupdate(p, add, m+1, r, rtt+1);maxnumb[rt] = MAX(maxnumb[rtt], maxnumb[rtt+1]);}int query(int L, int R, int l, int r, int rt){if(L<=l && R>=r){return maxnumb[rt];}int m = (l+r) >> 1, rtt = rt << 1, ans = 0;if(L <= m)ans = MAX(query(L, R, l, m, rtt), ans);if(R > m)ans = MAX(query(L, R, m+1, r, rtt+1), ans);return ans;}int main(){    int n, m, a, b;    while(~scanf("%d%d", &n, &m))    {        memset(maxnumb, 0, sizeof(maxnumb));        build(1, n, 1);        char ch;        for(int i=0; i<m; ++i)        {            getchar();            scanf("%c", &ch);            if(ch == 'Q') scanf("%d%d", &a, &b), printf("%d\n", query(a, b, 1, n, 1));            if(ch == 'U') scanf("%d%d", &a, &b), update(a, b, 1, n, 1);        }    }return 0;}

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