HDU -- 3275 -- Line Segment tree <again>

It also enhances the understanding of the delay mark of the line tree ~~

The question is very easy to give you a string of numbers 01. each operation must be performed on the number of K to flip it that is 0-> 1 1-> 0 is equivalent to the number of a range of [l, l + K-1] 0 and 1 swap operation

First, you must consider that the minimum number of operations must start from the leftmost.

Then, I find the leftmost 0 position in each query (FIND) operation. If it does not exist, I will return-1, indicating that all are 1.

Then on this [POs, POS + k-1] Flip operation here there is a judgment is if POS + k-1> N, it is equivalent to the failure to achieve all the results of 1 through flip.

Pay attention to the usage of Pushdown and pushup functions and the content of the function body... these are the essence. It is worth understanding ~ And I cannot understand it ..

 

1 // 0 indicates that the lantern is dark. 1 indicates that the lantern is bright. 2 # include <iostream> 3 # include <algorithm> 4 using namespace STD; 5 6 const int size = 100010; 7 char STR [size]; 8 struct data 9 {10 int L; 11 int R; 12 INT flag; 13 int numone, numzero; 14} tree [size * 4]; 15 16 void pushup (INT root) 17 {18 tree [root]. numone = tree [root <1]. numone + tree [root <1 | 1]. numone; 19 tree [root]. numzero = tree [root <1]. numzero + tree [root <1 | 1]. n Umzero; 20} 21 22 void Pushdown (INT root) 23 {24 tree [root <1]. flag ^ = 1; 25 tree [root <1 | 1]. flag ^ = 1; 26 swap (tree [root <1]. numzero, tree [root <1]. numone); 27 swap (tree [root <1 | 1]. numzero, tree [root <1 | 1]. numone); 28} 29 30 void build (INT root, int L, int R) 31 {32 int mid = (L + r)> 1; 33 tree [root]. L = L; 34 tree [root]. R = r; 35 Tree [root]. flag = 0; 36 IF (L = r) 37 {38 if (STR [l] = '1') 39 {40 tree [root]. numone = 1; 41 tree [root]. numzero = 0; 42} 43 else 44 {45 tree [root]. numone = 0; 46 tree [root]. numzero = 1; 47} 48 return; 49} 50 build (root <1, L, mid); 51 build (root <1 | 1, Mid + 1, r); 52 pushup (Root); 53} 54 55 void Update (INT root, int L, int R) 56 {57 int mid = (tree [root]. L + tree [root]. r)> 1; 58 If (tree [root]. L = L & tree [root]. R = R) 59 {60 swap (tree [root]. numzero, tree [root]. numone); 61 tree [root]. flag ^ = 1; 62 Return; 63} 64 if (tree [root]. flag) 65 {66 Pushdown (Root); 67 tree [root]. flag = 0; 68} 69 If (r <= mid) 70 update (root <1, L, R); 71 else if (L> = Mid + 1) 72 Update (root <1 | 1, L, R); 73 else 74 {75 Update (root <1, L, mid ); 76 Update (root <1 | 1, Mid + 1, R); 77} 78 pushup (Root); 79} 80 8 1 int query (INT root) 82 {83 int ans =-1; 84 If (tree [root]. L = tree [root]. r) 85 {86 return tree [root]. l; 87} 88 If (tree [root]. flag) 89 {90 Pushdown (Root); 91 tree [root]. flag = 0; 92} 93 If (tree [root <1]. numzero) 94 ans = query (root <1); 95 else if (tree [root <1 | 1]. numzero) 96 ans = query (root <1 | 1); 97 return ans; 98} 99 100 int main () 101 {102 cin. sync_with_stdio (false); 103 Int N, K, CNT, Pos; 104 bool flag; 105 while (CIN> N> K & (N | K) 106 {107 CNT = 0; 108 flag = true; 109 CIN >>( STR + 1); 110 build (1, 1, n); 111 If (tree [1]. numone = N) 112 {113 cout <0 <Endl; 114} 115 else if (! K) 116 {117 cout <-1 <Endl; 118} 119 else120 {121 while (1) 122 {123 pos = query (1 ); 124 If (Pos =-1) 125 break; 126 If (Pos + k-1> N) 127 {128 flag = false; 129 break; 130} 131 update (1, POs, pos + k-1); 132 + + CNT; 133} 134 If (FLAG) 135 cout <CNT <Endl; 136 else137 cout <-1 <Endl; 138} 139} 140 return 0; 141}

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Today:

Why are you ignoring me?

Do you dislike me?

Adults are tactically isolated from each other.

HDU -- 3275 -- Line Segment tree <again>