《Cracking the Coding Inteview》——第5章：位操作——题目8

 1 // 5.8 Given a byte array, set a consecutive bit segment to ‘1‘.
 2 #include <cstdio>
 3 #include <vector>
 4 using namespace std;
 5 
 6 typedef unsigned char byte;
 7 
 8 inline void setBit(vector<byte> &v, int i, int j, int w)
 9 {
10     v[i * w / 8 + j / 8] |= (1 << (j - (j >> 3 << 3)));
11 }
12 
13 inline int getBit(vector<byte> &v, int i, int j, int w)
14 {
15     return !!(v[i * w / 8 + j / 8] & (1 << (j - (j >> 3 << 3))));
16 }
17 
18 int main()
19 {
20     int n, w, h;
21     int x1, x2, y;
22     vector<byte> v;
23     int i, j;
24     
25     while (scanf("%d%d", &n, &w) == 2) {
26         h = n * 8 / w;
27         v.resize(n);
28         for (i = 0; i < n; ++i) {
29             v[i] = 0;
30         }
31         scanf("%d%d%d", &x1, &x2, &y);
32         
33         // boundary check is omitted.
34         for (i = x1; i <= x2; ++i) {
35             setBit(v, y, i, w);
36         }
37         
38         for (i = 0; i < h; ++i) {
39             for (j = 0; j < w; ++j) {
40                 putchar(‘0‘ + getBit(v, i, j, w));
41             }
42             putchar(‘\n‘);
43         }
44     }
45     
46     return 0;
47 }