Hdu 4576: Robot

RobotTime Limit: 8000/4000 MS (Java/Others) Memory Limit: 102400/102400 K (Java/Others) Total Submission (s): 1600 Accepted Submission (s ): 599 Problem DescriptionMichael has a telecontrol robot. one day he put the robot on a loop with n cells. the cells are numbered from 1 to n clockwise. at first the robot is in cell 1. then Michael uses a remote control to send m commands to the robot. A command wi Ll make the robot walk some distance. unfortunately the direction part on the remote control is broken, so for every command the robot will chose a direction (clockwise or anticlockwise) randomly with equal possibility, and then walk w cells forward. michael wants to know the possibility of the robot stopping in the cell that cell number> = l and <= r after m commands. inputThere are multiple test c Ases. each test case contains several lines. the first line contains four integers: above mentioned n (1 ≤ n ≤ 200), m (0 ≤ m ≤ 1,000,000), l, r (1 ≤ l ≤ r ≤ n ). then m lines follow, each representing a command. A command is a integer w (1 ≤ w ≤100) representing the cell length the robot will walk for this command. the input end with n = 0, m = 0, l = 0, r = 0. you shoshould not process this test case. outputFor each test case in the I Nput, you shoshould output a line with the expected possibility. output shoshould be round to 4 digits after decimal points. sample Input3 1 215 2 4 4120 0 0 0 Sample Output0.50000.2500 Source2013ACM-ICPC Hangzhou Division national invitational Competition Algorithm: simulation of the subject meaning: Robot round circle (1-n) walking, there are m commands, select the direction randomly and use the I command to walk the mi distance. Calculate the probability within the range of l to r. Train of Thought: simulation, no timeout. Construct two arrays. temp [] records the previous state. cnt [] records the current state (its initialization is 0) and moves temp [], which is not 0, then add it to the cnt [] at the destination location. Finally, the output is ans = temp [l] +... + temp [r]; Code:

# Include <stdio. h> # include <string. h >#define N 201 double cnt [N], temp [N]; int main () {int n, m, l, r, I, j, sum1, w, sum2, pos; double ans; while (scanf ("% d", & n, & m, & l, & r )! = EOF & (n + m + l + r) {memset (cnt, 0, sizeof (cnt); memset (temp, 0, sizeof (temp )); temp [1] = 1; for (I = 1; I <= m; ++ I) {scanf ("% d", & w ); // m w for (j = 1; j <= n; ++ j) {if (temp [j] = 0) continue; // clockwise pos = j + w % n; // determine the position if (pos> n) {pos-= n ;} cnt [pos] + = 0.5 * temp [j]; // counter-clockwise pos = j-w % n; if (pos <= 0) {pos ++ = n ;} cnt [pos] + = 0.5 * temp [j];} for (j = 1; j <= n; ++ j) {temp [j] = cnt [j]; cnt [j] = 0 ;}} sum1 = sum2 = 0; ans = 0; for (I = l; I <= r; ++ I) {ans + = temp [I];} printf ("%. 4lf \ n ", ans);} return 0 ;}