UVA1607Gates

//UVA1607Gates#include<cstdio>#include<cstdlib>#include<cstring>const int MAXN = 2e5 + 10;int m, n;struct Gate {int a, b, t;}Gates[MAXN];int solve(int k) {//将前k位信号置为0 for(int i = 1; i <= m; i++) {int a = Gates[i].a;int b = Gates[i].b;int va = a < 0 ? -a > k : Gates[a].t;//当a小于0时，说明i的信号一部分来源于总输入信号，//其中-a（正数）表示第-a位信号//当a大于0时，说明i的信号来源于前面一个编号为a的门处理后生成的信号//这段英文理解到吐血~~~~~，太晦涩 int vb = b < 0 ? -b > k : Gates[b].t;Gates[i].t = !(va && vb);//printf("Gates[%d].t = %d\n", i, Gates[i].t);}return Gates[m].t; }int Bsearch(int k) {int L = 1, R = n;while(L < R) {int M = L + (R - L) / 2;//printf("M = %d\n", M);if(solve(M) == k) R = M;//说明M位后面的信号对最终信号不产生影响 else  L = M + 1;//M位后面存在对本位产生影响的信号 }//二分，绝妙！！ return L; }int main() {int T;scanf("%d", &T);while(T--) {scanf("%d%d", &n, &m);        for(int i = 1; i <= m; i++) scanf("%d%d", &Gates[i].a, &Gates[i].b);int v0 = solve(0);int vn = solve(n);//printf("v0 = %d, vn = %d\n", v0, vn); if(v0 == vn) for(int i = 1; i <= n; i++) printf("0");else {int x = Bsearch(vn);for(int i = 1; i <= x - 1; i++) printf("0");printf("x");    for(int i = x + 1; i <= n; i++) printf("1");}printf("\n");}return 0;}/*13 6-1 -3 -1 -2 1 2 1 2 4 3 5 5*/