hdoj1754 线段树--单点更新
题目中文的，不解释了
维护一个最大值的线段树
1 #include <stdio.h> 2 3 #define lson l, m, rt<<1 4 #define rson m+1, r, rt<<1|1 5 6 const int maxn = 200000; 7 8 char cmd[2]; 9 int n, mNum, a, b, max[maxn<<2]; 10 11 int Max(int x, int y) 12 { 13 return (x>y ? x:y); 14 }/* Max */ 15 16 void BuildTree(int l, int r, int rt) 17 { 18 if (l == r) 19 { 20 scanf("%d", &max[rt]); 21 return ; 22 }/* End of If */ 23 24 int m = (l+r)>>1; 25 BuildTree(lson); 26 BuildTree(rson); 27 max[rt] = Max(max[rt<<1], max[rt<<1|1]); /* Push Up */ 28 }/* BuildTree */ 29 30 int Query(int L, int R, int l, int r, int rt) 31 { 32 if (L<=l && r<=R) 33 return max[rt]; 34 35 int ret=-1, m=(l+r)>>1; 36 37 if (L <= m) 38 ret = Max(ret, Query(L, R, lson)); 39 if (R > m) 40 ret = Max(ret, Query(L, R, rson)); 41 42 return ret; 43 }/* Query */ 44 45 void UpData(int p, int bi, int l, int r, int rt) 46 { 47 if (l == r) 48 { 49 max[rt] = bi; 50 return ; 51 }/* End of If */ 52 53 int m = (l+r)>>1; 54 55 if (p <= m) 56 UpData(p, bi, lson); 57 else 58 UpData(p, bi, rson); 59 60 max[rt] = Max(max[rt<<1], max[rt<<1|1]); /* Push Up */ 61 }/* UpData */ 62 63 int main() 64 { 65 while (~scanf("%d %d", &n, &mNum)) 66 { 67 BuildTree(1, n, 1); 68 for (int i=1; i<=mNum; ++i) 69 { 70 scanf("%s %d %d", cmd, &a, &b); 71 if (cmd[0] == 'Q') /* Query */ 72 printf("%d\n", Query(a, b, 1, n, 1)); 73 else /* UpData */ 74 UpData(a, b, 1, n, 1); 75 } 76 }/* End of While */ 77 78 return 0; 79 }
