计算几何-离散化

矩形覆盖

#include <iostream>#include <algorithm>using namespace std;struct SQ {int x1, y1;int x2, y2;} sq[201];int n;int X[401], Y[401];bool G[401][401];long long ans;int main() {cin >> n;for(int i=1; i<=n; i++) {cin >> sq[i].x1 >> sq[i].y1 >> sq[i].x2 >> sq[i].y2;X[i*2-1] = sq[i].x1;X[i*2] = sq[i].x2;Y[i*2-1] = sq[i].y1;Y[i*2] = sq[i].y2;}sort(X+1, X+2*n+1);sort(Y+1, Y+2*n+1);for(int i=1; i<=n; i++) {for(int x=1; x<2*n; x++) {if(sq[i].x2 <= X[x]) break;if(sq[i].x1 >= X[x+1]) continue;for(int y=1; y<2*n; y++) {if(sq[i].y2 <= Y[y]) break;if(sq[i].y1 >= Y[y+1]) continue;G[x][y] = true;}}}for(int x=1; x<2*n; x++) {long long s = X[x+1] - X[x];for(int y=1; y<2*n; y++) if(G[x][y]) ans += s * (Y[y+1] - Y[y]);}cout << ans << endl;return 0;}

区间覆盖

#include <iostream>#include <cstdio>#include <algorithm>using namespace std;struct Interval {int L, R;bool operator <(const Interval b) const { //重载运算符-按左端点比较 return L < b.L;}};Interval I[20001];int N, ans;int main() {int last;scanf("%d", &N);for(int i=1; i<=N; i++) scanf("%d%d", &I[i].L, &I[i].R);sort(I+1, I+N+1); //离散 last = -1e9-1;for(int i=1; i<=N; i++) { if(I[i].R <= last) continue; //if 当前区间被包含 if(I[i].L > last) ans += I[i].R - I[i].L;//if 与上个区间不重合 else ans += I[i].R - last;   //if 与上个区间有重合部分 last = I[i].R;}printf("%d\n", ans);return 0;}