#include <iostream>
#include <string>
int main(){
char p;
bool show_cleartext;
std::string input;
std::cout << "Would you like the output to show your original text? [y/n] \n";
while(true){
std::cin >> input;
if(input == "y"){show_cleartext = true; break;}
else if(input == "n"){show_cleartext = false; break;}
else std::cout << "[y/n] ? \n";
}
while(true){
// Promts for 'input' then displays input, reversed
std::getline(std::cin,input);
if(input == "quit")break;
for(int i = 0; i < (input.length()-1)/2; ++i){
p = input[input.length()-i-1];
input[input.length()-i-1] = input[i];
input[i] = p;
}
std::cout << input+'\n';
}
return 0;
}
每个while循环本身都很好。然而，包括它们两者会导致程序一旦超过第一个程序就会崩溃，即进入＆＃39; y＆＃39;或者＆＃39; n＆＃39;。
答案 0 :(得分：0)
当您询问用户input＆＃34;退出＆＃34;时，input尺寸变为＆＃34;＆＃34;因此，基本上input是一个空字符串，当你执行input.length()并且它等于0时，它会包围一个巨大的数字并导致崩溃。这是我从调试器中得到的，我建议你也使用它。
要解决此问题，请删除std::getline(std::cin,input);
重置input大小。
答案 1 :(得分：0)
我认为这个表达方式： p =输入[input.length（） - i-1]; 导致输入数组中的-1索引。 因此，如果您有0输入，则会收到错误。 也许试试这个：
legend.enhanced <- function (x, y = NULL, legend, fill = NULL, col = par("col"),
border = "black", lty, lwd, pch, angle = 45, density = NULL,
bty = "o", bg = par("bg"), box.lwd = par("lwd"), box.lty = par("lty"),
box.col = par("fg"), pt.bg = NA, cex = 1, pt.cex = cex,
pt.lwd = lwd, xjust = 0, yjust = 1, x.intersp = 1, y.intersp = 1,
adj = c(0, 0.5), text.width = NULL, text.col = par("col"),
text.font = NULL, merge = do.lines && has.pch, trace = FALSE,
plot = TRUE, ncol = 1, horiz = FALSE, title = NULL, inset = 0,
xpd, title.col = text.col, title.adj = c(0.5,0), seg.len = 2)
{
if (missing(legend) && !missing(y) && (is.character(y) ||
is.expression(y))) {
legend <- y
y <- NULL
}
mfill <- !missing(fill) || !missing(density)
if (!missing(xpd)) {
op <- par("xpd")
on.exit(par(xpd = op))
par(xpd = xpd)
}
title <- as.graphicsAnnot(title)
if (length(title) > 1)
stop("invalid 'title'")
legend <- as.graphicsAnnot(legend)
n.leg <- if (is.call(legend))
1
else length(legend)
if (n.leg == 0)
stop("'legend' is of length 0")
auto <- if (is.character(x))
match.arg(x, c("bottomright", "bottom", "bottomleft",
"left", "topleft", "top", "topright", "right", "center"))
else NA
if (is.na(auto)) {
xy <- xy.coords(x, y)
x <- xy$x
y <- xy$y
nx <- length(x)
if (nx < 1 || nx > 2)
stop("invalid coordinate lengths")
}
else nx <- 0
xlog <- par("xlog")
ylog <- par("ylog")
rect2 <- function(left, top, dx, dy, density = NULL, angle,
...) {
r <- left + dx
if (xlog) {
left <- 10^left
r <- 10^r
}
b <- top - dy
if (ylog) {
top <- 10^top
b <- 10^b
}
rect(left, top, r, b, angle = angle, density = density,
...)
}
segments2 <- function(x1, y1, dx, dy, ...) {
x2 <- x1 + dx
if (xlog) {
x1 <- 10^x1
x2 <- 10^x2
}
y2 <- y1 + dy
if (ylog) {
y1 <- 10^y1
y2 <- 10^y2
}
segments(x1, y1, x2, y2, ...)
}
points2 <- function(x, y, ...) {
if (xlog)
x <- 10^x
if (ylog)
y <- 10^y
points(x, y, ...)
}
text2 <- function(x, y, ...) {
if (xlog)
x <- 10^x
if (ylog)
y <- 10^y
text(x, y, ...)
}
if (trace)
catn <- function(...) do.call("cat", c(lapply(list(...),
formatC), list("\n")))
cin <- par("cin")
Cex <- cex * par("cex")
if (is.null(text.width))
text.width <- max(abs(strwidth(legend, units = "user",
cex = cex, font = text.font)))
else if (!is.numeric(text.width) || text.width < 0)
stop("'text.width' must be numeric, >= 0")
xc <- Cex * xinch(cin[1L], warn.log = FALSE)
yc <- Cex * yinch(cin[2L], warn.log = FALSE)
if (xc < 0)
text.width <- -text.width
xchar <- xc
xextra <- 0
yextra <- yc * (y.intersp - 1)
ymax <- yc * max(1, strheight(legend, units = "user", cex = cex)/yc)
ychar <- yextra + ymax
if (trace)
catn(" xchar=", xchar, "; (yextra,ychar)=", c(yextra,
ychar))
if (mfill) {
xbox <- xc * 0.8
ybox <- yc * 0.5
dx.fill <- xbox
}
do.lines <- (!missing(lty) && (is.character(lty) || any(lty >
0))) || !missing(lwd)
n.legpercol <- if (horiz) {
if (ncol != 1)
warning(gettextf("horizontal specification overrides: Number of columns := %d",
n.leg), domain = NA)
ncol <- n.leg
1
}
else ceiling(n.leg/ncol)
has.pch <- !missing(pch) && length(pch) > 0
if (do.lines) {
x.off <- if (merge)
-0.7
else 0
}
else if (merge)
warning("'merge = TRUE' has no effect when no line segments are drawn")
if (has.pch) {
if (is.character(pch) && !is.na(pch[1L]) && nchar(pch[1L],
type = "c") > 1) {
if (length(pch) > 1)
warning("not using pch[2..] since pch[1L] has multiple chars")
np <- nchar(pch[1L], type = "c")
pch <- substr(rep.int(pch[1L], np), 1L:np, 1L:np)
}
if (!is.character(pch))
pch <- as.integer(pch)
}
if (is.na(auto)) {
if (xlog)
x <- log10(x)
if (ylog)
y <- log10(y)
}
if (nx == 2) {
x <- sort(x)
y <- sort(y)
left <- x[1L]
top <- y[2L]
w <- diff(x)
h <- diff(y)
w0 <- w/ncol
x <- mean(x)
y <- mean(y)
if (missing(xjust))
xjust <- 0.5
if (missing(yjust))
yjust <- 0.5
}
else {
h <- (n.legpercol + (!is.null(title))) * ychar + yc
w0 <- text.width + (x.intersp + 1) * xchar
if (mfill)
w0 <- w0 + dx.fill
if (do.lines)
w0 <- w0 + (seg.len + x.off) * xchar
w <- ncol * w0 + 0.5 * xchar
if (!is.null(title) && (abs(tw <- strwidth(title, units = "user",
cex = cex) + 0.5 * xchar)) > abs(w)) {
xextra <- (tw - w)/2
w <- tw
}
if (is.na(auto)) {
left <- x - xjust * w
top <- y + (1 - yjust) * h
}
else {
usr <- par("usr")
inset <- rep_len(inset, 2)
insetx <- inset[1L] * (usr[2L] - usr[1L])
left <- switch(auto, bottomright = , topright = ,
right = usr[2L] - w - insetx, bottomleft = ,
left = , topleft = usr[1L] + insetx, bottom = ,
top = , center = (usr[1L] + usr[2L] - w)/2)
insety <- inset[2L] * (usr[4L] - usr[3L])
top <- switch(auto, bottomright = , bottom = , bottomleft = usr[3L] +
h + insety, topleft = , top = , topright = usr[4L] -
insety, left = , right = , center = (usr[3L] +
usr[4L] + h)/2)
}
}
if (plot && bty != "n") {
if (trace)
catn(" rect2(", left, ",", top, ", w=", w, ", h=",
h, ", ...)", sep = "")
rect2(left, top, dx = w, dy = h, col = bg, density = NULL,
lwd = box.lwd, lty = box.lty, border = box.col)
}
xt <- left + xchar + xextra + (w0 * rep.int(0:(ncol - 1),
rep.int(n.legpercol, ncol)))[1L:n.leg]
yt <- top - 0.5 * yextra - ymax - (rep.int(1L:n.legpercol,
ncol)[1L:n.leg] - 1 + (!is.null(title))) * ychar
if (mfill) {
if (plot) {
if (!is.null(fill))
fill <- rep_len(fill, n.leg)
rect2(left = xt, top = yt + ybox/2, dx = xbox, dy = ybox,
col = fill, density = density, angle = angle,
border = border)
}
xt <- xt + dx.fill
}
if (plot && (has.pch || do.lines))
col <- rep_len(col, n.leg)
if (missing(lwd) || is.null(lwd))
lwd <- par("lwd")
if (do.lines) {
if (missing(lty) || is.null(lty))
lty <- 1
lty <- rep_len(lty, n.leg)
lwd <- rep_len(lwd, n.leg)
ok.l <- !is.na(lty) & (is.character(lty) | lty > 0) &
!is.na(lwd)
if (trace)
catn(" segments2(", xt[ok.l] + x.off * xchar, ",",
yt[ok.l], ", dx=", seg.len * xchar, ", dy=0, ...)")
if (plot)
segments2(xt[ok.l] + x.off * xchar, yt[ok.l], dx = seg.len *
xchar, dy = 0, lty = lty[ok.l], lwd = lwd[ok.l],
col = col[ok.l])
xt <- xt + (seg.len + x.off) * xchar
}
if (has.pch) {
pch <- rep_len(pch, n.leg)
pt.bg <- rep_len(pt.bg, n.leg)
pt.cex <- rep_len(pt.cex, n.leg)
pt.lwd <- rep_len(pt.lwd, n.leg)
ok <- !is.na(pch)
if (!is.character(pch)) {
ok <- ok & (pch >= 0 | pch <= -32)
}
else {
ok <- ok & nzchar(pch)
}
x1 <- (if (merge && do.lines)
xt - (seg.len/2) * xchar
else xt)[ok]
y1 <- yt[ok]
if (trace)
catn(" points2(", x1, ",", y1, ", pch=", pch[ok],
", ...)")
if (plot)
points2(x1, y1, pch = pch[ok], col = col[ok], cex = pt.cex[ok],
bg = pt.bg[ok], lwd = pt.lwd[ok])
}
xt <- xt + x.intersp * xchar
if (plot) {
if (is.na(title.adj[2])) { title.adj[2] <- 0}
if (!is.null(title))
text2(left + w * title.adj[1], top - ymax, labels = title,
adj = c(title.adj[1], title.adj[2]), cex = cex, col = title.col)
text2(xt, yt, labels = legend, adj = adj, cex = cex,
col = text.col, font = text.font)
}
invisible(list(rect = list(w = w, h = h, left = left, top = top),
text = list(x = xt, y = yt)))
}
答案 2 :(得分：0)
问题在于std::getline(std::cin,input);的用法。 getline从istream中提取字符，直到达到分隔符或\n为止。在您的情况下，上一个std::cin的istream缓冲区包含\n。这会产生一个大小为0
其次，input.length()返回size_t，这是无符号整数类型。在这种情况下，input.length() - 1变为大数，循环条件的计算结果为true。随后，在input[input.length()-i-1];
为防止出现此错误，您可以在第二个std::getline(std::cin,input)循环中将std::cin >> input替换为while，或将std::cin >> input替换为第一个std::getline(std::cin,input)。