【算法可视化】搜索算法专题

运行平台

Algorithm Visualizer

选数

[NOIP2002 普及组] 选数

// 导入可视化库 {
const { Tracer, Array1DTracer, LogTracer, Layout, VerticalLayout } = require('algorithm-visualizer');
// }const N = 4, K = 3; //从包含4个元素的集合中选出3个数
let ans = 0 //方案数
const board =[3, 7, 12, 19];  //创建包含4个元素的一维数组
const chosen = [-1, -1, -1, -1]; //创建一维数组，初始为-1// 定义跟踪器 {
const boardTracer = new Array1DTracer('集合'); //集合，一维数组
const chosenTracer = new Array1DTracer('选中元素'); //选中元素，一维数组
const logger = new LogTracer('枚举过程');
Layout.setRoot(new VerticalLayout([boardTracer, chosenTracer, logger ]));boardTracer.set(board);
chosenTracer.set(chosen);
logger.println(`选数: 从${N}个元素中选出${K}个元素`);
Tracer.delay();
// }function validState(sum) {if(sum <= 1) return false;for (let i = 2; i <= sum / i; i ++)if(sum % i === 0) return false;return true;
}function dfs(t, last, sum) {if (t >= K) {let res = validState(sum)if(res) ans ++;// logger {logger.println(`所选${K}个数的和为${sum}`);if(res) logger.println(`${sum}是质数, 已找到${ans}组方案`);else logger.println(`${sum}不是质数`);logger.println('------------------------------------------------------------------');// }return;}for(let i = last + 1; i < N; i ++) {// visualize {logger.println(`第${t + 1}个数选择${board[i]}`);boardTracer.select(i);Tracer.delay();chosenTracer.patch(t, board[i])Tracer.delay();// }dfs(t + 1, i, sum + board[i])// visualize {boardTracer.deselect(i);Tracer.delay();chosenTracer.patch(t, -1)chosenTracer.depatch(t)Tracer.delay();// }}}// logger {
logger.println('开始执行');
// }
dfs(0, -1, 0);
// logger {
logger.println(`完成，一共有${ans}组答案`);
// }

八皇后 Checker Challenge

[USACO1.5] 八皇后 Checker Challenge

// import visualization libraries {
const { Tracer, Array2DTracer, Array1DTracer, LogTracer, Randomize, Layout, VerticalLayout } = require('algorithm-visualizer');
// }
function filledArray(length, value) {return Array(...Array(length)).map(Number.prototype.valueOf, value);
}const N = 6; //配置棋盘大小和初始状态
const board = (function createArray(N) {const result = [];for (let i = 0; i < N; i++) {result[i] = filledArray(N, 0);}return result;
}(N));
const queens = filledArray(N, -1);
const c = Randomize.Array1D({ N: N, value: () => Randomize.Integer({ min: 0, max: 0 }) }); //列状态
const u = Randomize.Array1D({ N: 2 * N, value: () => Randomize.Integer({ min: 0, max: 0 }) }); //对角线\状态
const v = Randomize.Array1D({ N: 2 * N, value: () => Randomize.Integer({ min: 0, max: 0 }) }); //对角线/状态// define tracer variables {
const boardTracer = new Array2DTracer('棋盘');
const queenTracer = new Array1DTracer('皇后所在行');
const logger = new LogTracer('算法过程');
Layout.setRoot(new VerticalLayout([boardTracer, queenTracer, logger]));boardTracer.set(board);
queenTracer.set(queens);
logger.println(`N皇后问题: ${N} X ${N}的棋盘放置 ${N} 个皇后`);
Tracer.delay();
// }let ans = 0
function dfs(x) {if (x >= N) {ans ++;// logger {logger.println(`递归到底. 所有皇后放置成功，第 ${ans} 组解为: [${queens.join(', ')}]`);logger.println('------------------------------------------------------------------');// }return;}for(let y = 0; y < N; y ++){if(c[y] === 0 && u[x + y] === 0 && v[y - x + N] === 0){// logger {logger.println(`将第 ${x} 行的皇后放到第 ${y} 列`);boardTracer.select(x, y);Tracer.delay();queenTracer.patch(x, y);Tracer.delay();// }c[y] = u[x + y] = v[y - x + N] = 1;queens[x] = y;dfs(x + 1);c[y] = u[x + y] = v[y - x + N] = 0;// logger {boardTracer.deselect(x, y);Tracer.delay();queenTracer.patch(x, -1); queenTracer.depatch(x, -1); Tracer.delay();// }}}
}// logger {
logger.println('开始执行');
// }
dfs(0);
// logger {
logger.println(`完成，一共有${ans}组解`);
// }

Lake Counting S

// import visualization libraries {
const {Tracer, Array2DTracer, LogTracer, Layout, VerticalLayout } = require('algorithm-visualizer');
// }
const n = 10, m = 12;
const G = [['W','.','.','.','.','.','.','.','.','W','W','.'],['.','W','W','W','.','.','.','.','.','W','W','W'],['.','.','.','.','W','W','.','.','.','W','W','.'],['.','.','.','.','.','.','.','.','.','W','W','.'],['.','.','.','.','.','.','.','.','.','W','.','.'],['.','.','W','.','.','.','.','.','.','W','.','.'],['.','W','.','W','.','.','.','.','.','W','W','.'],['W','.','W','.','W','.','.','.','.','.','W','.'],['.','W','.','W','.','.','.','.','.','.','W','.'],['.','.','W','.','.','.','.','.','.','.','W','.'],
];// define tracer variables {
const tracer = new Array2DTracer("Lake Counting S");
const logger = new LogTracer('广度优先搜索');
Layout.setRoot(new VerticalLayout([tracer, logger]));
tracer.set(G);
Tracer.delay();
// }const dx = [-1, -1, 0, 1, 1, 1, 0, -1];
const dy = [0, 1, 1, 1, 0, -1, -1, -1];
function bfs(x, y) {const Q = [];let node = [x, y]Q.push(node)tracer.patch(x, y, '.'); Tracer.delay();while(Q.length > 0){const node = Q.shift(); // dequeuex = node[0], y = node[1];for(let i = 0; i < 8; i ++){let a = x + dx[i], b = y + dy[i];if(a < 0 || a >= n || b < 0 || b >= m) continue;if(G[a][b] == '.') continue;G[a][b] = '.';Q.push([a, b]);// visualize {tracer.patch(a, b, '.');Tracer.delay();// }}}
}
// logger {
logger.println('开始执行');
// }
let ans = 0;
for(let i = 0; i < n; i ++)for(let j = 0; j < m; j ++)if(G[i][j] == 'W'){// logger {logger.println(`开始搜索${i}行${j}列开始的连通块`);// }ans ++;bfs(i, j);// logger {logger.println(`${i}行${j}列开始的连通块搜索结束`);// }}
// logger {
logger.println(`搜索完成，一共找到${ans}个水坑`);
// }