Find out what's wrong with the following program?

var cnt = 0;
function change(target, coins, usable) {
    coin = coins.shift();
    if(coins.length==0) {
        if(target/coin<=usable) {
            cnt += 1;
        }
    }
    else{
        for(let i=0; i<=target/coin; iPP) {
            change(target-coin*i, coins, usable-i);
        }
    }
}
change(1000, [500, 100, 50, 10], 15);
console.log(cnt);

algorithm topic link: https://max.book118.com/html/..

topic: at present, most people swipe their credit cards when they take the bus or subway. Today, however, more people are still paying in cash than expected. This topic is based on the change machine placed on the bus.

this machine can exchange banknotes for a combination of 10 yen, 50 yen, 100 yen and 500 yen coins, and there are enough coins for each type (because the minimum limit accepted by bus is 10 yen, so 1 yen and 5 yen coins are not provided).

When exchanging, the machine is allowed to exchange coins that can not be used in this payment. In addition, because it is inconvenient to exchange a large amount of change when taking the bus, the machine is only allowed to exchange up to 15 coins. For example, when you exchange a 1000 yen note, you cannot exchange it for a combination of 100 10 yen coins.

how many combinations will occur when you ask for 1000 yen notes? Note that the order in which the coins are redeemed is not taken into account.

var cnt = 0; function change(target, coins, usable) { let coin = coins.shift();//coin,for,target/coin<=usable. if(coins.length==0) { if(target/coin<=usable) { cnt += 1; } } else{ for(let i=0; i<=target/coin; iPP) { change(target-coin*i, coins.slice(), usable-i);//coins,shift. } } } change(1000, [500, 100, 50, 10], 15); console.log(cnt);

var cnt = 0, pagerCoin = 1000; // // a500 b100 c50 d10 // a+b+c+d <=15 // 500a+100b+50c+10d = 1000 // function getOneCoinsMaxNumber(pagerCoin,coin){ return Math.floor(pagerCoin/coin) } let abcd = []; // abcd for(let at,ai = (at=getOneCoinsMaxNumber(pagerCoin, 500)) > 15 ? 15 : at; ai >= 0; ai--) for(let bt,bi = (bt=getOneCoinsMaxNumber(pagerCoin,100)) > 15 ? 15 : bt; bi >= 0; bi--) for(let ct,ci = (ct=getOneCoinsMaxNumber(pagerCoin,50)) > 15 ? 15 : ct; ci >= 0; ci--) for(let dt,di = (dt=getOneCoinsMaxNumber(pagerCoin,10)) > 15 ? 15 : dt; di >= 0; di--) console.log(ai,bi,ci,di,abcd.push([ai,bi,ci,di])) // abcd console.log(abcd) let coins = [500,100,50,10] // let rule1 = arr => arr.reduce((init,item) => init+=item,0) let rule2 = arr => arr[0]*coins[0]+arr[1]*coins[1]+arr[2]*coins[2]+arr[3]*coins[3] // let d =abcd.filter(item => rule1(item) <= 15 && rule2(item) == 1000) console.log(d);

var A=[500,100,50,10];// var RT=[[2,0,0,0]];// var s=0x1AFF; // for(;s>0;s--){ // a0=s>>12; a1=(s>>8)&0xf; a2=(s>>4)&0xf; a3=s&0xf; if(a1>10 || a0+a1+a2+a3>15) continue; // if(a0*A[0]+a1*A[1]+a2*A[2]+a3*A[3] ===1000) RT.push([a0,a1,a2,a3]); } console.log(RT); var cnt=RT.length; console.log(cnt);//