PalindromeFinder.js

/*
	var Y_MAX = "99999";
	var X_MAX = "99999";
	initialize();
*/

function PalindromeFinder(x, y) {
    this.Y_MAX = x;
    this.X_MAX = y;
    this.doit = function(){
	start = new Date();
	var result = this.calc(this.X_MAX,this.Y_MAX);
	end = new Date();
	print(result[0]*result[1] + " = " + result[0] + " * " +result[1] +
              " ( " + (end.getTime() - start.getTime()) + " msec)");
    };
    this.calc = function(x, y) {
	var maxset = [0, 0];
	for (i=x; i>0; i--) {
	    if (maxset[0]*maxset[1] > (i*y)) {
		break;
	    }
	    for (k=y; k>0; k--) {
		//print("("+i+","+k+")");
		if (this.isPalindrome(i*k)) {
		    //print("isPalindrome!");
		    if (maxset[0]*maxset[1] < (i*k)) {
			maxset = [i, k];
		    }
		    break;
		}
	    }
	}
	return maxset;
    };
    this.isPalindrome = function(value) {
	value = new String(value);
	var center = value.length / 2;
	
	var first = value.substring(0, center);
	var last = value.substring(center, value.length);
	if (first == this.inverse(last)) {
	    return true;
	} else {
	    return false;
	}
    };
    this.inverse = function(value) {
	var rtnVal = "";
	for (index = value.length; index > 0 ; index--) {
	    rtnVal += value.charAt(index-1);
	}
	return rtnVal;
    };
}


var Palindrome = {
    doit: function(){
	start = new Date();
	var result = calc3(X_MAX,Y_MAX);
	end = new Date();
	print(result[0]*result[1] + " = " + result[0] + " + " +result[1] + " ( " + (end.getTime() - start.getTime()) + " msec)");
    },
    
    calc3: function(x, y) {
	var maxset = [0, 0];
	for (i=x; i>0; i--) {
	    if (maxset[0]*maxset[1] > (i*y)) {
		break;
	    }
	    for (k=y; k>0; k--) {
		//print("("+i+","+k+")");
		if (isPalindrome(i*k)) {
		    //print("isPalindrome!");
		    if (maxset[0]*maxset[1] < (i*k)) {
			maxset = [i, k];
		    }
		    break;
		}
	    }
	}
	return maxset;
    },
    
    calc2: function( x, y) {
	var maxset = [0,0];
	while (true) {
	    if (x < 1 || y < 1) {
		break;
	    }
	    // $("#calc").append(x + " * " + y + " = " + (x*y) + "<br>");
	    if (isPalindrome(x*y)) {
		if ((maxset[0]*maxset[1]) < (x*y)) {
		    maxset = [x, y];
		}
		x--;
		y = Y_MAX;
	    } else {
		if (x == y) {
		    x--;
		    y = Y_MAX;
		} else {
		    y--;
		}
	    }
	}
	return maxset;
    },
    
    calc: function(x, y) {
	var maxset = [];
	(function f(x, y) {
	    //$("#calc").append(x + " * " + y + " = " + (x*y) + "<br>");
	    if (x < 0) {
		// xが0以下になったら終了
		return;
	    }
	    if (y < 0) {
		return f(x-1, Y_MAX);
	    }
	    if (isPalindrome(x*y)) {
		if ((maxset[0]*maxset[1]) < (x*y)) {
		    maxset = [x,y];
		}
	    } else {
		f(x, y-1);
	    }
	})(x, y);
	return maxset;
    },
    
    isPalindrome: function(value) {
	value = new String(value);
	var center = value.length / 2;
	for (var i=0;i<center;i++) {
	    //print(value);
	    if (value.charAt(i)!=value.charAt(value.length-(i+1))) {
		//print(value  + " => " + value.charAt(i) + " , " + value.charAt(value.length-(i+1)) );
		//print("return false");
		return false;
	    }
	}
	//print("return true");
	return true;
    },
    
    isPalindrome2: function(value) {
	value = new String(value);
	var center = value.length / 2;
	
	var first = value.substring(0, center);
	var last = value.substring(center, value.length);
	if (first == inverse(last)) {
	    return true;
	} else {
	    return false;
	}
    },
    
    inverse: function(value) {
	var rtnVal = "";
	for (index = value.length; index > 0 ; index--) {
	    rtnVal += value.charAt(index-1);
	}
	return rtnVal;
    }
};