一道线段树的题目，由于之前没怎么做过线段树的题目，这道题我觉得还是有点小难的
首先将x坐标排序，然后找相邻的x坐标之间的最大y值和最小y值，这些矩形是要覆盖x,x+1坐标的，然后将yMax,yMin分散到线段树上，并用一个值标记哪些节点被分布了，最后查找一遍就可以了。
代码如下：
1 #include <iostream> 2 #include <algorithm> 3 #include <cstring> 4 using namespace std; 5 6 int X_axle[20000]; 7 8 struct node 9 { 10 int xLow,xHigh,yLow,yHigh; 11 }Point[10010]; 12 struct node1 13 { 14 int low,high; 15 int value; 16 }seg[300]; 17 18 int xCount; 19 int pCount; 20 int num,ans; 21 22 void init1(int r,int l,int h) 23 { 24 seg[r].value = 0; 25 seg[r].low = l; 26 seg[r].high = h; 27 28 if(l == h) 29 { 30 return; 31 } 32 int m = (l+h) >> 1; 33 init1(r*2,l,m); 34 init1(r*2+1,m+1,h); 35 } 36 37 void init(int& x1,int& y1,int& x2,int& y2) 38 { 39 if(x1 > x2) swap(x1,x2); 40 if(y1 > y2) swap(y1,y2); 41 X_axle[xCount ++] = x1; 42 X_axle[xCount ++] = x2; 43 Point[pCount].xLow = x1; 44 Point[pCount].xHigh = x2; 45 Point[pCount].yLow = y1; 46 Point[pCount ++].yHigh = y2; 47 } 48 49 bool cmp(const int& a,const int& b) 50 { 51 return a < b; 52 } 53 54 void seg_tree(int root,int low,int high) 55 { 56 if(seg[root].low == low && seg[root].high == high) 57 { 58 seg[root].value = num; 59 return; 60 } 61 int mid = (seg[root].low + seg[root].high) >> 1; 62 if(high <= mid ) 63 { 64 seg_tree(root*2,low,high); 65 }else if(low > mid) 66 { 67 seg_tree(root*2+1,low,high); 68 }else 69 { 70 seg_tree(root*2,low,mid); 71 seg_tree(root*2+1,mid+1,high); 72 } 73 } 74 75 void get_ans(int root,int low,int high) 76 { 77 if(seg[root].value == num) 78 { 79 ans += (seg[root].high - seg[root].low +1); 80 return; 81 } 82 if(seg[root].low == seg[root].high) return; 83 int mid = (low + high) >> 1; 84 get_ans(root*2,low,mid); 85 get_ans(root*2+1,mid+1,high); 86 } 87 int main() 88 { 89 int x1,y1,x2,y2; 90 init1(1,0,100); 91 num = 0; 92 93 while(cin >> x1 >> y1 >> x2 >> y2) 94 { 95 xCount = 0; 96 pCount = 0; 97 init(x1,y1,x2,y2); 98 99 while(cin >> x1 >> y1 >> x2 >> y2) 100 { 101 if(x1 == -1 || x2 == -2) 102 { 103 break; 104 } 105 init(x1,y1,x2,y2); 106 } 107 sort(X_axle,X_axle+xCount,cmp); 108 109 int ans_value = 0; 110 for(int i = 0;i < xCount-1;i ++) 111 { 112 if(X_axle[i] == X_axle[i+1]) continue; 113 num ++; 114 115 for(int j = 0;j < pCount;j ++) 116 { 117 if(Point[j].xLow <= X_axle[i] && Point[j].xHigh >= X_axle[i+1]) 118 { 119 seg_tree(1,Point[j].yLow+1,Point[j].yHigh); 120 } 121 } 122 ans = 0; 123 get_ans(1,0,100); 124 ans_value += ans * (X_axle[i+1] - X_axle[i]); 125 } 126 cout << ans_value << endl; 127 if(x1 == -2) 128 { 129 break; 130 } 131 } 132 return 0; 133 }